WmmmMm 

wggmBm 

JHH 
■HH 



ANALYSIS of 



A*ri>MM PRODUCTS 



FFMftM and BEAM 



LIBRA RY OjvCON GRESS. 

Chap*^V_ Copyright No. 

Slielf___,__L_4 ^ " 



UNITED STATES OF AMERICA. 



It 



ANALYSIS OF MILK AND MILK PRODUCTS 



LEFFMANN AND BEAM. 



EXAMINATION OF WATER 

FOR SANITARY AND TECHNICAL PURPOSES. 

BY HENRY LEFFMANN. 

Third Edition. i2mo. 154 pages. Illustrated. $1.25. 



A COMPEND OF CHEMISTRY, 

INORGANIC AND ORGANIC, INCLUDING URINARY ANALYSIS. 

BY HENRY LEFFMANN. 

Especially Adapted to Students in Medicine and Dentistry. 

Fourth Edition. Revised. 
Price $0.80. Interleaved for taking Notes, $1.25. 



Sanitary Relations of the Coal-Tar Colors. 

BY THEODORE WEYL. 

AUTHORIZED TRANSLATION BY HENRY LEFFMANN. 

i2mo. 154 pages. $1.25. 



Progressive Exercises in Practical Chemistry. 

A LABORATORY HANDBOOK. 

BY HENRY LEFFMANN. 

Illustrated. Second Edition. i2mo. Cloth, $1.00. 



P. BLAKISTON, SON 



ANALYSIS 



MILK AND MILK PRODUCTS 



HENRY LEFFMANN, M.A., M.D., 



WILLIAM BEAM, M.A., M.D. 



SECOND EDITION, REVISED AND ENLARGED, 
WITH ILL US TEA I IONS. 



PHILADELPHIA: ^ & £ ^ /> -"' / 

P. BLAKISTON, SON & CO., 

I O I 2 WALNUT ST R EET. 
1896. 



Copyright, 1896, by P. Blakiston, Son & Co. 






PRESS OF WM. F. FELL & CO., 

1220-24 Sansom Street, 

philadelphia. 



PREFACE. 



The first edition of this book was quite favorably received 
by competent critics, but it was noted that the analysis of 
butter and cheese was too briefly treated. It is hoped 
that this objection has been removed in the present edition. 
A large amount of matter has been added concerning those 
topics ; all the processes of analysis which have practical 
value in detecting butter adulteration have been given in 
detail, many from the latest publication of the A. O. A. C. 
A large addition has been made to the Chapter on Cheese, 
and a brief note on the fermented milk beverages. Other 
features have not been neglected. Considerable matter 
has been added in relation to the determination of lactose, 
among which maybe mentioned Wiley and E well's recently 
described process of double dilution and polarization, 
and Allen's manipulation of Pavy's solution. The tables 
for determining total solids by Hehner and Richmond's 
formula have been recalculated according to Richmond's 
corrected formula. 

Concerning the rapid method of fat-extraction with 
which our names are connected, we desire to say that the 
taking out of a patent was rendered necessary by some 
business arrangements over which we had no control and 
which, at that time, seemed to require such action to pro- 
tect a reputable merchant from serious loss. The amount 



paid was small and an offer has since been made to repur- 
chase the patent for the sum originally paid for it, the 
intention being to make its use free, but the negotiations 
failed. We also deem it proper to say that the originality 
of the discovery rests only on the chemicals employed in 
liberating the fat. The application of centrifugal machinery 
to the separation of liquids of different specific gravity 
dates from more than a generation ago and cannot be now 
allowed as an invention. We have regretted that a foreign 
chemist has appropriated, without acknowledgment, the 
special features of our method. 

As in the first edition, we have relied largely upon the 
contributions published in the " Proceedings of the Asso- 
ciation of Official Agricultural Chemists," and in The 
Analyst. H. L. 

W. B. 

7/5 Walnut Street, Philadelphia, 
September, 1896. 



CONTENTS. 



Nature and Composition of Milk. page 
Formation and Ingredients of Cow's Milk — Colos- 
trum — Milk of Various Animals — Properties and 
Decompositions of Milk — Skimmed Milk — Butter- 
milk — Whey, 9-17 

Analytic Processes. 

Specific Gravity — Total Solids — Ask — Fat — Pro- 

teids — Sugar — Milk Adulterants, 18-52 

Data for Milk Inspection. 

Variations in Composition— Sanitary Relations, . 53-63 

Milk Products. 

Condensed Milk — Butter — Cheese — Fermented 
Products, 64-106 

Appendix. 

Table for Correcting Specific Gravity — Table for 
Calculating Total Solids — Table for Calculating 
Lactose — Supplementary Notes — Index, .... 107-120 



NATURE AND COMPOSITION OF MILK. 

Milk, the nutritive secretion of nursing mammals, con- 
sists of water, fat, proteids, sugar, and mineral matters. 
Cow's milk, being of the greatest importance to the analyst, 
will receive the largest share of attention, and will be under- 
stood to be meant in all cases, unless otherwise stated. 

With rare exceptions, the secretion of milk takes place 
only as a result of pregnancy and delivery at term, and 
continues for a variable period. The chemistry of its 
formation is not entirely understood. The organic in- 
gredients do not exist in appreciable quantities in the 
blood, and must, therefore, be elaborated by specific 
secretory action. 

Fat. — This occurs in globules varying from .0015 mm. 
to .005 mm. in diameter, in a condition which prevents 
spontaneous coalescence. According to Gutzeit, the aver- 
age size of the globules is affected by many circumstances, 
such as change of weather, of food, or locality. During 
the whole time of lactation they regularly diminish in 
diameter. Among cows of the same breed their average 
size, extending over the whole lactiferous period, is fairly 
constant. The properties exhibited by the fat-globules 
have been regarded as indicating the existence of a mem- 
brane surrounding them, but they may be explained with- 
out such an assumption. If an envelope of any kind exists, 
it probably is merely a liquid one, such as the film of a 
soap-bubble. 

B 



IO NATURE AND COMPOSITION OF MILK. 

The fat of milk consists of a mixture of the ethers of 
tritenyl (C 3 H 5 ), but is peculiar among animal fats in con- 
taining a notable proportion of acid-radicles with a small 
number of carbon atoms. Thus, about 91 per cent, con- 
sists of stearin, palmitin, and olein, and the remaining 
nine per cent, of butyrin and caproin along with minute 
amounts of caprin, myristin and caprylin, and some others. 
The exact arrangement of these constituents is not known, 
but the weight of opinion is that milk-fat is not a mixture 
of simple fats, but that several acid radicles are united to 
the same tritenyl molecule. 

The following results of the analysis of a sample of but- 
ter-fat are given by Dr. Bell : — 

Per cent. 

Butyric acid, 6.1 

Caproic, caprylic, and capric acids, .... 2.1 
Myristic, palmitic, and stearic acids, . . .49.4 

Oleic acid, 36.1 

Glycerol (calculated), 12.5 

According to Duclaux, the mean composition of butter- 
fat is probably : — 

Per cent. 

Palmitin, stearin, olein, with traces of my- 
ristin and butin, 91.5 

Butyrin, 4.2 

Capronin, 2.5 

Caprylin, caprinin, laurin (traces), .... 1.8 

100.0 
Proteids. — The nature of the proteids of milk has been 
much discussed, but it is now generally conceded that 
there are at least three forms, casein, albumin, and globu- 
lin, the casein being present in by far the greater amount, 
and the globulin as traces only. 

Casein. — Casein is in large part, at least, in a gelatinous 



(colloidal) form, probably in combination with calcium 
phosphate. It is precipitated from this condition by 
acids, rennet, magnesium sulfate, and other substances. 
Acids precipitate the casein by breaking up the combina- 
tion with calcium phosphate. The action of rennet is 
more complex. Hammersten has shown that it is depend- 
ent upon the presence of calcium salts; thus, if the curd 
precipitated by dilute acid be dissolved in dilute alkali 
and the solution neutralized, it is unaffected by rennet, 
but regains its coagulability by the addition of a solu- 
tion of a calcium salt or, what amounts to the same thing, 
a little of the whey from which the casein was precipitated. 
It appears that rennet splits the casein into two proteids, 
one of which is precipitated in the curd. 

Halliburton uses the term " caseinogen " to designate 
the form in which the casein exists when in solution or pre- 
cipitated by acids, and reserves the term casein for the curd 
produced by rennet. 

Films of proteid matter occur abundantly in milk, for 
which reason it is distinctly opaque, even when all but a 
trace of the fat has been removed by centrifugal action. 

The albumin of milk appears to be a distinct form, and 
is called lactalbumin. It is not precipitated by dilute 
acids, but is coagulated by heating to 7o°-75° C. The 
proportion in cow's milk is usually from 0.35 to 0.50 per 
cent., but colostrum may contain much larger proportions. 

Sebelien gives the composition of lactalbumin as fol- 
lows : — 

Carbon, 5 2 - I 9 



Hydrogen, 

Nitrogen, 

Oxygen, 

Sulfur, 



7.18 
15-77 



i-73 



12 NATURE AND COMPOSITION OF MILK. 

Globulin is present only in minute amounts in normal 
milk, but colostrum may contain as much as eight per 
cent. It is coagulated on heating. 

Lactose. — This is the sugar of milk and is peculiar to it. 
Richmond discovered in the milk of the gamoose a sugar 
not identical with lactose; probably extended investiga- 
tion of the milk of various animals will show the existence 
of other forms of milk-sugar. Crystallized lactose has 
the composition C 12 H 22 O n -f- H 2 0. By heating to 125 C. 
the water is expelled. It has a specific rotatory power of 
-f- 52.5, which is independent of concentration. Freshly 
prepared solutions exhibit higher rotatory power, but after 
twenty-four hours standing, at ordinary temperatures, or 
immediately on boiling, the rotatory power is reduced to 
the figure given above. Alkaline solutions of copper salts are 
readily reduced by lactose at the boiling temperature. 
Richmond has shown that continued heating of a solution 
of milk-sugar causes caramelization and diminution of the 
rotatory power, but the reducing power to alkaline copper 
solution is not sensibly affected even after heating for two 
hours. In contact with yeast, lactose undergoes alcoholic 
fermentation, but with difficulty. It undergoes the lactic 
fermentation, however, very readily under the influence 
of certain microbes. When milk is evaporated rapidly to 
dryness, as in the determination of total solid residue, the 
milk-sugar is left in the anhydrous state. 

Citric acid is a normal constituent of the milk of various 
animals. In human milk, the quantity is about 0.5 gram 
to the liter, in cow's milk from 1 to 1.5 grams. It is not 
dependent on the citric acid present in the food. 

Minute amounts of nitrogenous bases and a starch - 
liquefying enzym also occur. 



COLOSTRUM. 



13 



The ash of milk has the following composition : — 

Ca, .... 
Mg, ... 

Fe, 0002 

K, 146 

Na, 082 



.113 per cent, (of milk) 
.0126 



P0 4 

so 4 , 

CI, 
CO, 



.263 

traces 

.169 

.020 



Colostrum. — This term is applied to the milk secreted 
in the early stages of lactation. It usually differs marked- 
ly from ordinary milk. It contains characteristic struc- 
tures known as colostrum corpuscles. These are ameboid 
bodies several times as large as the fat-globules. They are 
present for a variable period — three to fourteen days — but 
may persist much longer. Colostrum usually contains 
much less fat than fully developed milk, but a larger pro- 
portion of proteids, the increase being principally in the 
albumin, though Emmerling has found over 8 per cent, of 
globulin. The large proportion of albuminous matter 
causes colostrum to coagulate on boiling. Lactose is in 
small amount and is said to be largely replaced by another 
carbohydrate. 

The following analysis is the average of the colostrum of 
22 cows. (Eugling.) 

Fat, . . 
Casein, . 
Albumin, 



Sugar, 
Ash 

Total solids 

Colostrum is usually acid to litmus. 



3-37 

4-83 
I5-85 
2.48 
1. 78 



28.31 



14 



NATURE AND COMPOSITION OF MILK. 




COLOSTRUM. 1 5 

Normal milk is an opaque, white or yellowish-white fluid, 
with an odor recalling that of the animal, and a faint 
sweet taste. The opacity is due partly to the fat-globules, 
but when these are entirely removed the liquid does not 
become transparent. The reaction of freshly drawn milk 
is amphoteric to litmus, that is, it turns the red paper blue 
and blue paper red. The specific gravity varies between 1028 
and 1035. It usually undergoes a gradual augmentation 
(sometimes termed Recknagel's phenomenon) for a con- 
siderable time after the sample has been drawn. The 
increase may amount to two units. The specific gravity 
becomes stationary in about five hours if the milk be 
maintained at a temperature below 15 C, but at a higher 
temperature it may require twenty-four hours to acquire 
constancy. The change is not dependent on the escape of 
gases, and is believed to be due to some molecular modifi- 
cation of the casein, possibly under the influence of an 
enzym. 

Unless collected with special care and under conditions 
of extreme cleanliness, milk always contains bacteria and 
animal matter of an offensive character, such as epithelium, 
blood and pus cells, particles of feces and soil. Many 
minute organisms, especially bacteria, propagate with great 
rapidity in milk and produce changes in its composition. 
Some specific organisms, such as the Spi?'illum cholera, 
multiply to only a limited extent in ordinary milk, being 
hampered by the bacteria normally present, but when 
introduced into sterilized milk increase with great rapidity. 

At ordinary temperature milk soon undergoes decompo- 
sition under the influence of the microbes present, by 
which the milk-sugar is converted principally into lactic 
acid, and the proteids partly decomposed and partly coag- 



1 6 NATURE AND COMPOSITION OF MILK. 

ulated. The liquid becomes sour and the fat is enclosed 
in the coagulated casein. 

In the initial stages of decomposition the proteids fre- 
quently undergo transformations into substances which are 
the cause of the violent poisonous effects occasionally pro- 
duced by ice cream and other articles of food into the 
preparation of which milk enters. 

Boiling produces coagulation of the albumin, some 
caramelization of the sugar, and develops a greater facility 
of coalescence on the part of the fat globules. Enzyms 
and most microbes are destroyed. The skin which forms 
on the surface of boiling milk is composed largely of 
casein. It is due probably to the more rapid evaporation 
at the surface of the liquid. 

Partial freezing produces a concentration of the milk 
solids in the part remaining liquid, while the solid portion 
is deficient in them. The normal condition can, there- 
fore, be restored only by thawing the entire mass and 
mixing thoroughly. 

Richmond has published the following analyses as show- 
ing how great a difference may exist between the ice and 
liquid portion. The ice amounted to about 10 per cent. : — 

Ice. Liquid. 

Water, 96. 23 86.62 

Fat, 1.23 4.73 

Sugar, 1.42 4.95 

Proteids, 91 3.90 

Ash, 21 .80 

Specific gravity, - . . 1009 T °34-5 

When milk is allowed to stand, some of the fat rises 
gradually and forms a rich layer, constituting cream. 
The proportion of cream depends on several conditions. 



COLOSTRUM. 1 7 

The amount formed in a given time cannot be taken as a 
measure of the richness of the milk. Water added to 
milk causes a more rapid separation of the cream. When 
milk is subjected to centrifugal action, a larger proportion 
of cream is quickly obtained, nearly all of the fat being 
removed. The following figures, given by D'Hout as aver- 
ages, show the effect of the centrifugal action : — 

Whole milk. Separated milk. Cream. 



Specific gravity, 
Total solids, , 
Sugar, .... 
Casein, . . . 
Ash, 


. 1032 
. 14.10 

• 4-7o 

• 3-5° 
0. 7q 


Fat, 


v / y 
• 5-05 



IO34 


1015 


9.6 


26.98 


5-°5 


3-3 2 


3.62 


2.02 


0.78 


058 


0. 20 


21.95 



Buttermilk is the residue after removal of the butter by 
churning. Vieth gives the following figures : — 

Total solids. Fat. Solids not fat. Ash. 

9.03 0-63 8.40 O.70 

8.02 O.65 7.37 I.29 

ic.70 o-54 10.16 0.82 

The whey left after the precipitation of the curd by 
rennet or acid still contains a notable amount of proteids. 
The following analyses are by C. B. Cochran (J". A. C. S., 
i893» P- 347): — 



M 


ILK 






Whey. 




Total solids. 


Solids not fat. 


Total solids 


Proteids removed. 


9.27 




9- T 3 


6.62 




2-5* 


9.27 




9*3 


6.1 




3°3 


14.05 




3-35 


6.62 




2 -33 


7.71 




7.61 


5-98 




163 


8.91 




8.71 


6.50 




2.21 



The whey of any given milk has the same composition, 
whether taken from the original milk, skimmed milk, or 
cream. 



ANALYTIC PROCESSES. 

The specific gravity determination is to be made only after 
the spontaneous rise has ceased. This will require about 
five hours, after the milk is drawn, if it has been kept 
below 1 5 C, but at a higher temperature it will be neces- 
sary to allow at least twelve hours. For all other deter- 
minations the milk must be analyzed as soon as possible, as 
it decomposes very rapidly at ordinary temperatures. The 
following figures, published by Bevan, show that a con- 
siderable loss in total solids may occur in twenty-four 
hours : — 





Total solids. 


Loss. 


Evaporated immediately, . . 


• u-73 




" after 24 hours, . 


• 10 79 


0.94 


" 48 " • 


• 10.38 


i-35 


" " 120 " 


. 9.42 


2.31 



The decomposition is very irregular and it is not possible 
to determine, by estimation of the lactic acid or other 
products, the original composition of the milk. The 
pipet used for taking a portion for analysis should have a 
wide opening, that no cream may be retained when the 
pipet is discharged. 

SPECIFIC GRAVITY. 

Air bubbles are held rather tenaciously by milk, and 

care must be taken in mixing, preparatory to taking the 

specific gravity, to avoid as far as possible the enclosure of 

18 



SPECIFIC GRAVITY. 1 9 

air, and to allow sufficient time for the escape of any 
bubbles that may be present. Determinations of specific 
gravity of milk are understood to be taken at the tempera- 
ture of 6o° F., and samples at temperatures materially 
different from this should be brought to it. If at a few 
degrees above or below 6o°, it will suffice to take the 
gravity at once and obtain the correct figures by reference 
to Table A. The specific gravity of normal milk varies 
between 1028 and 1035. Since the specific gravity can 
be raised by the abstraction of fat (skimming) and restored 
by the addition of water, the figure taken alone cannot be 
relied upon as an index of the character of the sample, 
but in conjunction with the figure for fat or for total solids 
it is of great value, as a check on the results furnished by 
other determinations. 

The simplest method of determining specific gravity is 
by the lactorfensimeter, a delicate and accurately graduated 
hydrometer. The instrument must be immersed carefully 
so as not to wet the stem above the point at which it will 
rest. The instrument should be tested by immersion in 
distilled water at 15 C. 

The indications furnished by the lactodensimeter are 
sufficiently accurate for most purposes, but its employment 
necessitates a considerable amount of the sample. 

More accurate determination can be made by the 
Westphal balance. This is a delicate steelyard with a 
counterpoised plummet, displacing 5 c. c. The plummet 
being immersed in the milk, the equilibrium is restored by 
weights, the value of which can be directly expressed in 
figures for the specific gravity. 

The principle of the Westphal balance may be applied 
by means of an analytic balance and a plummet. The 



ANALYTIC PROCESSES. 




latter may conveniently consist of a short thermometer, or 
a thick glass rod, having a bulk of from 5 to 10 c. c. It 
is suspended from the hook of 
the balance by a fine platinum 
wire and its weight ascertained. 
It is then immersed in distilled 
water at 6o° F. and the loss in 
weight noted. The figure so 
obtained is the weight of a 
bulk of water equal to that of 
the plummet. This having 
been determined, the specific 
gravity of a milk maybe found 
by immersing the plummet in it and noting the loss in 
weight, which, divided by the loss in pure water, gives 
the specific gravity. 

The pyknometer or specific-gravity bottle furnishes a 
means of accurate determination and is especially appli- 
cable when only a small amount of liquid is available. It 
is a small flask furnished with a perforated glass stopper. 
It is provided with a counterpoise equal to the empty 
flask and the weight of water that it carries is indicated. 
These data may, of course, be easily verified, and any 
error noted. The milk should be first brought to the 
proper temperature, the bottle completely filled, the 
stopper inserted, and the excess which flows out through 
the perforation and around the sides of the stopper re- 
moved by bibulous paper. The weight of milk divided by 
that of the water which the flask will hold at the same 
temperature gives the specific gravity. 



TOTAL SOLIDS. 2 1 

TOTAL SOLIDS. 

This determination is made by evaporation in a shallow, 
flat-bottomed dish, preferably of platinum, from 7 to 8 cm. 
in diameter. The milk must be spread evenly in a thin 
layer. If the ash is also to be determined, about 5 grams 
should be accurately weighed in the dish, evaporated 
rapidly to apparent dryness over the water-bath and the 
heating continued in the water-oven until the weight be- 
comes practically constant, which will require about three 
hours. If the evaporation be slow, some decomposition 
occurs and the residue is brown, but if the larger portion 
of the water be evaporated quickly, a white residue is ob- 
tained. When the ash is not to be determined, it is more 
convenient to follow the method suggested by Richmond, 
using 1 to 2 grams, accurately weighed. The drying can 
be completed in about one and a half hours. 

When a higher degree of accuracy is desired, Babcock's 
method (A. O. A. C.) may be employed as follows : — 

Provide a hollow cylinder of perforated sheet metal 60 
mm. long and 20 mm. in diameter, closed 5 mm. from 
one end by a disk of the same material. The perforations 
should be about 0.7 mm. in diameter and the same distance 
apart. Fill the cylinder loosely with from 1.5 to 2.5 grams 
of freshly ignited woolly asbestos free from fine or brittle 
material. Cool in a desiccator and weigh. Introduce a 
weighed quantity of milk (about 4 gm.) and dry at 100 
C. to constant weight. 

The residue will serve for the determination of the fat. 

When rigid accuracy is not essential, it will suffice to 
measure the portion of milk taken for this and other deter- 
minations. Vieth uses a pipet graduated to deliver 5 



2 2 ANALYTIC PROCESSES. 

grams and finds that, working with whole and skimmed 
milk, under the ordinary variations of temperature, the 
error will not exceed o. i on the total solids and is less on 
the fat. 

A good plan is to use a 5 c. c. pipet and to wash out 
that which adheres to the glass with a little water. The 
specific gravity of the milk being known, the amount 
taken can be calculated. The milk should be as near 6o G 
F. as possible. 

ASH. 

The residue from the determination of total solids is 
heated cautiously over the Bunsen burner, until a white 
ash is left. The result obtained in this manner is apt to 
be slightly low from loss of sodium chlorid. This may be 
avoided by heating the residue sufficiently to char it, ex- 
tracting the soluble matter with a few c.c. of water, and 
filtering (using paper extracted with hydrofluoric acid). 
The filter is added to the residue, the whole ashed, the fil- 
trate then added, and the liquid evaporated carefully to 
dryness. The ash of normal milk is about 0.7 per cent, 
and faintly alkaline; if the milk be watered the ash will 
be less. The ash of milk does not exactly represent the 
salts present in the milk. On ignition, the phosphorus of 
the casein is oxidized to phosphoric acid, which decom- 
poses the carbonates formed by the ignition of the organic 
salts of the milk, and liberates carbonic acid. A marked 
degree of alkalinity and effervescence with hydrochloric 
acid will suggest the addition of a carbonate. 

The method of the A. O. A. C. is as follows : In a 
weighed dish put 20 c.c. of milk from a weighing bottle, 
add 6 c.c. of nitric acid, evaporate to dryness, and burn at 
a low red heat until all form carbon. 



FAT. 

The method introduced by Wanklyn for the determina- 
tion of fat by extracting it with ether from the total 
solid residue, has been found to give results 0.5 per cent, 
or more below the correct figure, and is therefore not 
described. 

Adams' Method. — This consists essentially in spread- 
ing the milk over absorbent paper, drying, and extracting 
the fat in a Soxhlet apparatus ; the milk is distributed in an 
extremely thin layer, and by a selective action of the paper 
the larger portion of the fat is left on the surface. It is 
essential that the paper contain no materials soluble in the 
liquid used for extraction. A paper, manufactured espec- 
ially for this purpose by Schleicher & Schuell, is obtain- 
able in strips of suitable size. Each of these yields to 
ether from .001 to .002 gram of extract, which may usually 
be disregarded. 

The procedure is as follows : Five c.c. of the milk are dis- 
charged into a beaker 5 cm high and 3.5 cm. in diameter. 
The charged beaker is weighed, and a strip of the paper, 
which has been rolled into a coil, thrust into it. In a few 
minutes the paper will absorb nearly the whole of the milk. 
The coil is then carefully withdrawn, and stood dry end 
downward on a sheet of glass. 

With a little dexterity, all but the last fraction of a 
drop will be absorbed by the paper. The beaker is again 
weighed and the milk taken found by difference. It is of 
importance to take up the whole of the milk from the 
beaker, as the paper has a selective action, removing the 
watery constituents by preference over the fat. The 
charged paper is placed in the water-oven on a glass plate, 



24 



ANALYTIC PROCESSES. 



milk-end upward, and dried. Usually about one hour is 
sufficient. It is inserted in a Soxhlet continuous-extraction 
apparatus, the tared flask of which should have a capacity 
of about 150 c. c. and contain about 75 c. c. 
of anhydrous, alcohol-free ether, or petroleum 
spirit boiling at about 45 ° C. Heat is applied 
to the flask by means of a water bath, or 
by resting it on a piece of asbestos paper, 
which is heated by a small flame. After the 
coil has received at least ten or twelve wash- 
ings, the flask is detached, the ether removed 
by distillation, and the fat dried by heating in 
an air oven at about 105 C, and occasionally 
blowing air through the flask. After cooling, 
the flask is wiped with a piece of silk, allowed 
to stand ten minutes, and weighed. 

Richmond states that to perform a rigidly 
accurate determination attention to the follow- 
ing points is necessary : The ether must be 
anhydrous (drying over calcium chlorid and 
distilling is sufficient). Schleicher & Schuell's 
fat-free papers should be used and one should 
be extracted without any milk on it, as a tare 
for the others. Four or five hours' extraction 
is necessary, and the coils should be well dried before ex- 
traction is begun. 

Thimble-shaped cases made of fat-free paper are now 
obtainable and are convenient for holding the absorbent 
material on which the milk is spread. The fine texture 
prevents undissolved matter escaping. A case may be 
used repeatedly. Sour milk must be thinned with ammo- 
nium hydroxid before taking the portion for analysis. 



25 



When the Babcock method has been used for determining 
the total solids, the cylinder and contents maybe placed in 
the Soxhlet tube and extracted with ether in the usual 
way. In addition to weighing the fat, after evaporation of 
the ether, it may be determined by difference, by drying 
the extracted cylinder at ioo° C. and weighing. A still 
higher accuracy is secured by performing all the drying 
operations in an atmosphere of hydrogen. 

Werner-Schmid Method. — This is a very satisfac- 
tory and rapid method for the determination of fat and is 
especially suitable for sour milk. 

Ten c. c. of the milk are measured into a long test-tube of 
50 c. c. capacity, graduated to tenths 
c. c, and 10 c. c. of strong hydro- 
chloric acid added, or the milk may be 
weighed in a small beaker and washed 
into ' the tube with the acid. After 
mixing, the liquid is boiled one and a 
half minutes, or the tube may be 
corked and heated in the water bath 
from five to ten minutes, until the 
liquid turns dark brown. It must 
not be allowed to turn black. The 
tube and contents are cooled in 
water, 30 c. c. of well-washed ether 
added, shaken, arid allowed to stand 
until the line of acid and ether is dis- 
tinct. The cork is taken out, and a 
double-tube arrangement, like that of ^ 

the ordinary wash-bottle, inserted. 
The stopper of this should be of cork and not of rubber, 
since it is difficult to slide the glass tube in rubber, and 
c 




2 6 ANALYTIC PROCESSES. 

there is a possibility, also, of the ether acting on the rubber 
and dissolving it. The lower end of the exit-tube is ad- 
justed so as to rest immediately above the junction of the 
two liquids. The ethereal solution of the fat is then blown 
out and received in a weighed flask. Two more portions 
of ether, 10 c. c. each, are shaken with the acid liquid, 
blown out, and added to the first. The ether is then dis- 
tilled off, and the fat dried and weighed as above. 

Leffmann-Beam Method. — Among the processes for 
the rapid determination of fat those employing centrifugal 
machines have been most satisfactory. The following 
method can be applied very cheaply, both as regards the 
original cost of the apparatus and of the chemicals required 
for the test, the latter being usually no inconsiderable item 
when many tests are made. The manipulation is very 
simple. 

Machines arranged for either two, four, six, eight, or 
twelve bottles are manufactured. The process is covered 
by patent in the United States, which has been assigned 
to J. E. Lonergan, of Philadelphia. 

The test-bottles have a capacity of about 30 c. c, and 
are provided with a graduated neck, each division of which 
represents one-tenth per cent, by weight of butter-fat. 

Fifteen c. c. of the milk are measured into the bottle, 3 
c. c. of a mixture of equal parts of amyl alcohol and strong 
hydrochloric acid added, mixed, the bottle filled nearly 
to the neck with concentrated sulfuric acid and the liquids 
mixed by holding the bottle by the neck and giving it a 
gyratory motion. The neck is now filled to about the 
zero point with a mixture of sulfuric acid and water pre- 
pared at the time. It is then placed in the centrifugal 
machine, which is so arranged that when at rest the bot- 



FAT. 2 7 

ties are in a vertical position. If only one test is to be 
made, the equilibrium of the machine is maintained by 
means of a test-bottle, or bottles, filled with a mixture of 
equal parts of sulfuric acid and water. After rotation for 
from one to two minutes, the fat will collect in the neck 
of the bottle and the percentage may be read off". It is 
convenient to use a pair of dividers in making the read- 
ing. The legs of these are placed at the upper and lower 
limits respectively of the fat, allowance being made for the 
meniscus ; one leg is then placed at the zero point and the 
reading made with the other. Several years' experience 
by analysts in various parts of the world has shown that 
with properly graduated bottles the results are reliable. 
As a rule, they do not differ more than one-tenth of i 
per cent, from those obtained by the Adams process, and 
are generally even closer. Richmond, as the result of an 
exhaustive series of investigations, draws the following 
conclusions : — 

i. As variations in the sulfuric acid and fusel- oil may 
slightly influence the result, it is well to obtain large quan- 
tities of these at a time, and by a few preliminary experi- 
ments fix the factor necessary to convert scale readings 
into percentages of fat. 

2. It is advisable to use the same strength of acid (94 to 
96 per cent. H 2 S0 4 is convenient). This may be esti- 
mated either by converting a known quantity into ammo- 
nium sulfate, drying at ioo° C, and weighing; titrating 
the acidity .with decinormal barium hydroxid, using 
methyl-orange as indicator, and then igniting, and weigh- 
ing the non-volatile matter (correcting for the barium sul- 
fate formed); or deducing the strength from the density 
(hydrometers are rarely of sufficient accuracy, and a pyc- 



2 8 ANALYTIC PROCESSES. 

nometer should be used), and correcting by subtracting 
twice the weight of the non-volatile matter. 

3. If it be necessary to perform the experiment when 
the atmospheric temperature is high, the milk and acid 
should be cooled beforehand, or if this is not practicable, 
the acid should be added in small portions (2 c. c.) at a 
time, and the bottle shaken between each addition, or a 
weaker acid may be used. 

4. About half to three-quarters of a minute's revolution, 
at the rate of from 1200 to 1500 revolutions a minute, has 
been found the most convenient in practice. The machine 
has not been found dangerous at this speed ; but, if wished, 
a longer period of revolution at a slower speed is equally 
efficacious. 

For accurate work the factor for correcting the reading 
on each of the bottles should be determined by comparison 
with the figures obtained by the Adams or other standard 
process. 

Cream is to be diluted to exactly ten times its volume, 
the specific gravity taken, and the liquid treated as a milk. 
Since in the graduation of the test-bottles a specific gravity 
of 1030 is assumed, the reading must be increased in 
proportion. 

A more accurate result may be obtained by weighing 
in the test-bottle about 2 c. c. of the cream and diluting 
to about 15 c. c. The reading obtained is to be multi- 
plied by 15.45 and divided by the weight in grams of 
cream taken. 

The mixture of amyl alcohol and hydrochloric acid 
seems to become less satisfactory when long kept. It is 
best, therefore, not to make up large amounts at once. 
The mixture should be clear and not very dark in color. 



FAT. 29 

Samples of amyl alcohol that produce a black solution 
with hydrochloric acid are unsuitable. (See Appendix.) 

Calculation Method. — Several investigators have 
proposed formulae by which when any two of the data, 
specific gravity, fat, and total solids are known, the third 
can be calculated. Since fairly accurate determinations of 
the fat and specific gravity can be made by rapid and sim- 
ple methods, the formulae become very serviceable and 
should always be used to check the results. That of 
Hehner and Richmond has been almost exclusively used. 

It is as follows : — 

F = .859 T— .2186 G 
in which F represent the fat, T the total solids, and G the 
specific gravity. This formula will suffice for ordinary 
milks, but for poor skim milks it has been found necessary 
to modify it as follows : — 

F = .859 T — .2186 G — .05 {- — 2.5) 

This correction is to be applied only when G divided by 
T exceeds 2.5. 

In these formulae, G represents the last two units of the 
specific gravity and any decimal. Thus, if the observed 
specific gravity be 1029.5, G wl ^ be 2 9-5- 

A ready means of applying the formula is by the use of 
Richmond's slide-rule. This has three scales, two of 
which, for fat and total solids respectively, are marked on 
the body of the rule, while that for the specific gravity is 
placed on the sliding portion. 

The divisions are as follows : — 

Total solids, 1 inch divided into tenths 

Fat, 1. 164 inches " " " 

Specific gravity, . . . 0.254 " " " halves 



30 ANALYTIC PROCESSES. 

The rule is employed by adjusting the arrow point to the 
graduation corresponding to the fat found, when the figure 
for the total solids will coincide with that for the observed 
specific gravity. This instrument does not take into con- 
sideration the necessary correction for poor skim milks, but 
the error from this cause will in no case exceed .08 per 
cent, of fat and may usually be disregarded. 

It has been found that the fat calculated by the above 
formula is slightly higher than the actual amount. Re- 
cently, Richmond has proposed a new formula — 

G 

T— .2625 (1000 4^;;) -f 1.2 F 
1000 

and finds the results obtained by it to agree much better 
with accurate analysis. 

The formula may be simplified as follows, 

^ + |F + , 4 

and the result will not differ in extreme cases more than 
.02 from those calculated from the more complex formula. 
Results calculated from this formula will be found in 
Table B. 

A milk-scale to express the same relation may be con- 
structed on which 1 per cent, total solids = 1 inch, 1 per 
cent, of fat = 1.2 inches, and 1 degree of gravity = % inch; 
if the zero on the fat scale be placed on a line with 5 per 
cent, on the total-solids scales, the arrow will be in its cor- 
rect position : 0.14 (1) inch below 20 degrees on the spe- 
cific gravity scale. By placing an arrow 0.14 inch below 
the present arrow, existing milk scales will give a near 
approximation. 



TOTAL PROTEIDS. 3 1 

TOTAL PROTEIDS. 

This determination is best made by calculation from the 
figure for total nitrogen obtained by Gunning's modifica- 
tion of Kjeldahl's process. The reagents and apparatus 
required are as follows: — 

Standard sulfuric acid. — This should be about deci- 
normal, the exact value being determined by precipitating 
a measured volume with barium chlorid, collecting and 
weighing the barium sulfate under the usual precautions. 

Standard barium hydroxid. — This should be about deci- 
normal. The volumetric relation between this solution and 
the standard sulfuric acid must be accurately determined, 
employing phenolphthalein as an indicator. 

Acid potassium sulfate mixture. — One part of pure potas- 
sium sulfate is heated with two parts of sulfuric acid (strictly 
C. P.) until the potassium sulfate is dissolved. The mixture 
is semi-solid when cold but may be readily liquefied by 
warming. 

Sodium hydroxid solution. — A saturated solution in water. 
A good quality of pulverized sodium hydroxid is now sold 
under various trade names, e.g., "Lewis' Lye," "Banner 
Lye," and these will be found satisfactory. 

Digestion and distillation flask. — This has a body capable 
of holding about 550 c. c, and a cylindrical neck about 
18 cm. in length and 25 cm. in diameter. It is supported 
on wire-gauze or asbestos, and the mouth may be covered 
by a watch-glass or funnel during the digestion. For dis- 
tilling, a well-fitting rubber stopper with delivery tube 
should be attached. The tube should be of the same 
diameter as the condensing tube, and should have one or 
two bulbs, about 4 cm. in diameter, to prevent any solution 



3 2 



ANALYTIC PROCESSES. 



being carried over by spurting. It should project slightly 
below the stopper and be cut off obliquely. 

Condenser. — The condensing tube must be of block tin 
of an external diameter of about one centimeter. At least 
30 centimeters of its length should be in contact with the 
cooling water. The junction of the glass and tin tube is 
made by a short, close-fitting rubber tube, and the tubes 
are so bent as to slope toward the distilling flask. The 
lower end of the tin tube is connected by a short rubber 
tube with a glass bulb-tube which dips below the surface of 
a measured volume (20 c. c.) of the standard sulfuric acid 
in an Erlenmeyer flask of about 300 c. c. capacity. 

Five c. c. of the milk are weighed or measured into the 
flask and evaporated to dryness over the water-bath ; 30 c.c. 
of the acid potassium sulfate mixture are added and heated 
over the Bunsen burner. At first, frothing occurs and 
white fumes escape, consisting chiefly of water-vapor. To 
prevent loss of acid, the neck of the flask is now fitted 
with a funnel which is covered with a watch glass. This will 
cause the acid to condense and run back into the flask. 
The operation is finished when the liquid is colorless, which 
generally requires about an hour. When cold, the contents 
of the flask are diluted with about 200 c. c. of water, 
several pieces of ignited pumice dropped in, and sufficient 
of the sodium hydroxid solution (about 50 c. c.) added to 
make the mixture strongly alkaline. It should be poured 
down the side of the flask so that it does not mix at once 
with the acid. The flask is now connected with the con- 
denser and the contents mixed by shaking. The liquid is 
now distilled until the whole of the ammonium hydroxid 
is collected, which will usually be the case when 150 c. c. 
have passed over. The receiver and short tube dipping in 



TOTAL PROTEIDS. 



33 



it are then detached and the distillate titrated to determine 
the amount of acid unneutralized. From this the amount 
of ammonium hydroxid can be calculated, and the nitrogen 
in this multiplied by 6.38 will give the figure for the total 
proteids. 

The A. O. A. C. recommends an indicator prepared as 
follows: Three grams of cochineal are digested for several 
days at room temperature in a mixture of 50 c. c. of strong 
alcohol and 200 c. c. of water. The filtered solution is 
used. 

The Ritthausen Method for Total Proteids.— 
This method depends on precipitation by copper sulfate 
and sodium hydroxid. It is applicable only to fully de- 
veloped milks; the proteids of colostrum and whey are 
only partially precipitated. The reagents are : — 

Copper sulfate solution. — 34.639 grams of pure crystal- 
lized copper sulfate are dissolved and made up to 500 c. c. 

Sodiu7?i hydroxid solution. — About 12 grams are dissolved 
in 500 c. c. of water. 

Ten grams of the milk are placed in a beaker, diluted 
with 100 c.c. of distilled water, 5 c. c. of copper sulfate 
solution added, and thoroughly mixed. The sodium 
hydroxid solution is then added drop by drop, with con- 
stant stirring, until the precipitate settles quickly and the 
liquid is neutral, or at most very feebly acid. An excess 
of alkali will prevent the precipitation of some of the 
proteids. 

The reaction should be tested on a drop of the clear 
liquid, withdrawing it by means of a rod, taking care not 
to include any solid particles. When the operation is 
correctly performed, the precipitate, which includes the 
fat, settles quickly, and carries down all of the copper. 



34 ANALYTIC PROCESSES. 

It is washed by decantation with about ioo c. c. of water, 
and collected on a filter (previously dried at 130 C. and 
weighed in a weighing bottle). The portions adhering to 
the sides of the beaker are dislodged with the aid of a 
rubber-tipped rod. The contents of the filter are washed 
with water until 250 c. c. are collected, which are mixed 
and reserved for the determination of the sugar as de- 
scribed below. The water in the precipitate is removed 
by washing once with strong alcohol, and the fat by six or 
eight washings with ether. The Soxhlet apparatus may 
be used for this purpose. The washings being received in 
a weighed flask, the determination of the fat may be 
made by evaporating the ether with the usual precau- 
tions. 

The residue on the filter, which consists of the pro- 
teids in association with copper hydroxid, is washed with 
absolute alcohol, which renders it more granular, and then 
dried at 130 C. in the air bath. It is weighed in a weigh- 
ing bottle, transferred to a porcelain crucible, incinerated, 
and the residue again weighed. The weight of the filter 
and contents, less that of the filter and residue after igni- 
tion, gives the weight of the proteids. The results by this 
method are slightly high, since copper hydroxid does not 
become completely converted into copper oxid at 130 C. 

Richmond and Boseley {Analyst, 1893) modify this pro- 
cess N by diluting the milk to 200 c. c, adding a little 
phenolphthalein, and neutralizing any acidity by the 
cautious addition of dilute sodium hydroxid solution, 
then adding from 2.0 to 2.5 c. c. of the copper sulfate 
solution. The precipitate is allowed to settle, washed, and 
estimated as above. 



CASEIN AND ALBUMIN. 35 

CASEIN AND ALBUMIN. 

Twenty c. c. of the milk are mixed with 40 c. c. of a 
saturated solution of magnesium sulfate and powdered 
magnesium sulfate stirred in until no more will dissolve. 
The precipitate of casein and fat, including the trace of 
globulin, is allowed to settle, filtered, and washed several 
times with a saturated solution of magnesium sulfate. The 
filtrate and washings are saved for the determination of 
albumin. The filter and contents are transferred to a flask 
and the nitrogen determined by the method described above. 
The nitrogen so found multiplied by 6.38 gives the casein. 

The filtrate and washings from the determination of casein 
are mixed, the albumin precipitated by a solution of tan- 
nin, filtered, and the nitrogen in the precipitate determined 
as above. The same factor is used. 

On account of the difficulty of washing the precipitated 
casein, we prefer to proceed as follows : 20 c. c. of the milk 
are mixed with saturated magnesium sulfate solution and 
the powdered salt added to saturation. The mixture is 
washed into a graduated measure with a small amount of 
the saturated solution, mixed, the volume noted, and 
allowed to stand until the separation takes place. As much 
as possible of the clear portion is drawn off with a pipet 
and passed through a dry filter. An aliquot portion of the 
filtrate is taken, the albumin precipitated by a solution of 
tannin, and the nitrogen in the precipitate determined as 
above. 

The casein is found by subtracting the figure for albu- 
min from that for total proteids. 

For the separation of the proteids in milk, the methods 
of Hoppe-Seyler and Ritthausen have been much used. 



36 ANALYTIC PROCESSES. 

The casein is precipitated by the addition of acetic acid to 
the diluted milk, the action being rendered complete, in 
the one case, by raising the temperature to 40 C, and in 
the other by passing a current of carbon dioxid through 
the mixture at ordinary temperatures. L. L. Van Slyke 
(J. A. C. S., Vol. xv, p. 635), as the result of a series of 
investigations, finds these methods to give practically 
identical results and recommends the following procedure 
for the separation and estimation of the casein and albu- 
min : — 

Casein. — Weigh out about ten grams of milk, dilute in 
a beaker with about 90 c. c. of water at 4o°-42° C, and 
add at once 1.5 c. c. of a solution containing 10 per cent, 
of acetic acid by weight. Stir with a glass rod, let stand 
three to five minutes, decant on to a filter, wash two or 
three times with cold water by decantation, transfer the pre- 
cipitate completely to the filter, and wash it once or twice. 
The washed precipitate and filter paper are then treated by 
the Kjeldahl-Gunning method for the determination of 
nitrogen, and the estimation made in the usual manner. 
To calculate the nitrogen into an equivalent amount of 
casein, multiply by the factor 6.38. 

Albumin. — The filtrate from the separated casein is 
heated in boiling water for ten or fifteen minutes. The 
coagulated albumin is collected in a filter, washed, and the 
filter and precipitate treated by the Kjeldahl-Gunning 
method. The amount of nitrogen multiplied by 6.38 gives 
the amount of albumin. 

Remaining nitrogen compounds. — The remaining com- 
pound or compounds of nitrogen are determined by differ- 
ence, subtracting from the amount of total nitrogen com- 
pounds the sum of the casein and albumin. 

The albumin of condensed milk is partly coagulated by 
the heat employed in its manufacture. When magnesium 
sulfate is added, therefore, to precipitate the casein, the 
coagulated albumin will be carried down at the same time 



SUGAR. 37 

and only the soluble albumin will be found in the nitrate. 
Faber {Analyst, 1889) nas applied this fact to the detection 
of the previous heating of a sample of milk. Usually, only 
about one-third of the albumin is found uncoagulated in 
condensed milk. 

SUGAR. 

The following method, due to Soxhlet, employs a Feh- 
ling's solution, made as required, by mixing equal parts of 
the following solutions: — 

Copper sulfate solution. — 34.639 grams of pure crystal- 
lized copper sulfate are dissolved in distilled water and 
made up to 500 c. c. 

Alkaline tai'trate solution. — One hundred and seventy- 
three grams of pure sodium potassium tartrate, and 51 
grams of sodium hydroxid of good quality, are dissolved 
and made up to 500 c. c. 

One hundred c. c. of the mixed filtrate obtained as de- 
scribed on p. ^ are brought to boiling, 50 c. c. of boil- 
ing Fehling's solution added, and the boiling continued for 
six minutes. The precipitate is allowed to settle for a 
short time, and the supernatant liquid poured through a 
filter. About 50 c. c. of boiling water are added to the 
residue, and the heating continued for a minute or two. 
The precipitate is then conveyed to the filter, washed with 
boiling water, with alcohol, and finally with a small quan- 
tity of ether. The filter and contents are dried in the 
water oven, the precipitate removed to a tared porcelain 
crucible, the filter held over the crucible and burnt to ash, 
which is added to the precipitate, and the cuprous oxid 
converted into cupric oxid by strong ignition, for five or 
ten minutes, over the Bunsen burner. 



38 ANALYTIC PROCESSES. 

The amount of copper reduced under the conditions de- 
tailed above is not directly proportional to the milk-sugar 
present. Table C shows the amounts of milk-sugar (C 12 
H 22 O u -j- H 2 O) equivalent to given weights of cupric 
oxid. The volumes of Fehling's solution and sugar solu- 
tion must conform strictly to the figures given above. 

Many of the English analysts prefer to make volumetric 
determinations by means of Pavy's modification of Feh- 
ling's solution, in which strong ammonium hydroxid is used 
to maintain the cuprous oxid in solution and thus permit 
nicer determination of the end-reaction. Allen has in- 
vestigated with great care the value of this method for 
determining the form of glucose that occurs in urine and 
finds that considerable variation may be made in the formula 
of Pavy's solution without the oxidizing ratio being appre- 
ciably affected, but it will be best to adhere closely to a 
particular formula in milk determinations. A description 
of the process is given in connection with analysis of con- 
densed milks. 

The determination of sugar may also be made by means 
of the polarimeter after removal of the fat and proteids. 
This may be effected by means of a nitric acid solution of 
mercuric nitrate as suggested by Wiley. 

The mercuric nitrate solution is prepared by dissolving 
mercury in twice its weight of nitric acid of 1.42 sp. gr. 
and adding to the solution five volumes of water. 

Sixty c. c. of the milk are placed in a 100 c. c. flask and 
10 c. c. of the mercuric solution added. The flask is filled 
to the mark with water, well shaken, and the liquid filtered 
through a dry filter. The filtrate, which will be perfectly 
clear, may be examined at once in the polarimeter. Several 
readings should be made and the average taken. 



SUGAR. 39 

It is to be noted that the actual volume of the sugar- 
containing solution is ioo c. c, less the space occupied by 
the precipitated proteids and fat. The volume of fat is 
found by multiplying the weight in grams by 1.075 an< ^ 
the proteids by multiplying the weight by 0.8. 

For example : — 

Sp. gr. of milk 1030, fat 4 per cent., proteids 4 per cent. 
Milk taken = 60 X 1.03 = 61.80 gms. 
The weight of fat = 4 per cent, of 61.80 == 2.47 gms. 
The weight of proteids = 4 per cent, of 6 1.80 r= 2.47 gms. 
The volume of fat = 2.47 X 1-075 == 2-65 c. c. 
The volume of proteids = 2.47 X .8 — 1.97 c. c. 
The bulk of the sugar containing liquid is therefore 
100 — (2.65 -j- 1.97) = 95.38 c. c. 

In order to avoid the calculation involved in taking 
60 c. c. of the milk as given above, an amount may be 
employed which is a simple multiple of the standard quan- 
tity to be used in the polarimeter at hand. Thus, for 
instruments adjusted so that 16.19 grams of sucrose (20.56 
grams of milk-sugar) in 100 c. c. of the solution produce a 
rotation of 100 degrees on the percent, scale, 61.68 grams 
(20.56 X 3) maybe weighed out directly for the. purpose and 
made up to 100 c. c. plus the volume occupied by the fat 
and proteids, the latter being calculated as above. The 
sugar-containing liquid will then be exactly 100 c. c, and 
the reading on the polarimeter divided by three will give 
the percentage of hydrated milk-sugar direct if a 200 
mm. tube be employed. With a 400 mm. tube or 500 
mm. tube the reading is to be divided by 6 or 7.5 
respectively. 

Polarimeters. — A discussion of the construction of the 
various forms of polarimeters and of the optical principles 



40 ANALYTIC PROCESSES. 

involved, would be beyond the scope of this work. The 
most economic instruments are the so-called half-shadow 
instruments, using the sodium flame, and they are the most 
satisfactory. They are so arranged that the field is divided 
into semicircles which are equally illuminated when the 
instrument registers zero. On the introduction of the 
tube carrying the sugar solution, the illumination becomes 
unequal and the angular rotation of the analyzer, which is 
required to restore the original condition, measures the 
rotation which has been caused by the sugar. Most instru- 
ments are furnished with two scales, one showing the rota- 
tion in angular degrees and the other expressing per cent, 
directly. The latter reads to ioo when a certain fixed 
quantity of the material has been dissolved in water and 
diluted to ioo c. c. 

The specific rotatory power of a substance is the amount of 
rotation of the plane of polarized light, in angular degrees, 
produced by a solution containing one gram of the substance 
in i c. c, examined in a column i decimeter long. 

It is expressed by the following formula, in which 

S is the specific rotatory power for light of wave length 
corresponding to the D line of the spectrum (sodium 
flame). 

a is the angular rotation observed, 

c is the concentration of the solution (weight in grams, 
in ioo c. c. of the liquid), and 

/is the length of the tube in decimeters. 

- ioo a 

cT~ 

Calculation of the amount of sugar corresponding to the 
observed rotation may be made by substitution in the for- 
mula. 



SUGAR. 41 

The specific rotatory power of milk-sugar is unaffected 
by the concentration within the limits encountered in ordi- 
nary milk-analysis. It is slightly affected by temperature, 
being decreased by about .075 angular degree for each 
successive rise of one degree Centigrade. The specific 
rotatory power at 20 C. is 52. 5 ° when observed by the 
sodium flame. 

The employment of an arbitrary factor for correcting 
for the volume of precipitate may be avoided by the so- 
called method of " double dilution/' in which two solutions 
of different volume are compared. With the higher class 
of polarimeters, the determinations may be easily made 
within one-tenth per cent. The following is a summary 
of the method given by Wiley and Ewell (y. A. C. S., 
1895, p. 428) who recommend it strongly. The instrument 
used. was the new triple-field shadow polarimeter made by 
Schmidt and Haensch, which permits readings to be made 
within 0.05 per cent. 32.91 grams of lactose dissolved in 
100 c. c. gave a reading of 100. The amount of milk taken 
was double this quantity, that is, 65.82 grams, which were 
placed in a 100 c.c. flask, 10 c.c. of the acid mercuric nitrate 
added, the flask filled to the mark, the contents well mixed, 
filtered, and polarized. A similar quantity of the milk was 
placed in a 200 c. c. flask and treated in the same way. 
The true polarization is obtained by dividing the product 
of the readings in the two flasks by their difference. Thus 
in the paper above noted the following experiments are 
recorded : — 

Reading in 200 Reading in 100 Apparent per True per cent. 
c. c. flask. c. c. flask. cent. lactose. lactose. 

IO 15 20.84 5.21 4.95 

The polarimeter used had a tube 4 decimeters long. 

D 



42 ANALYTIC PROCESSES. 

The figure for apparent percentage is obtained by dividing 
the reading of the small flask by 4. The true percentage 
is obtained by multiplying 10.15 by 20.84, dividing by 
their difference (10.69), and taking one-fourth this quo- 
tient. 

Birotation. — When freshly dissolved in cold water, milk 
sugar shows a higher rotation than that given above. By 
standing, or immediately on boiling, the rotatory power 
falls to the point mentioned. In preparing solutions from 
the solid milk-sugar, care must be taken to bring them to 
the boiling point previous to making up a definite volume. 
This precaution is unnecessary when operating upon milk. 



MILK ADULTERANTS. 

Water. — The addition of water to milk is usually de- 
tected by the diminution in the amount of solids. It was 
formerly supposed that normal milk does not contain ni- 
trates, and since these are almost universally present in 
surface and subsoil waters, it was suggested that the ap- 
plication of some of the delicate tests for nitrates would 
detect the addition of water, but Bevan has shown that 
pure milk may contain nitrates, and Richmond obtained 
a reaction for nitrates from the milk of a cow to which had 
been administered a very small quantity of niter. 

The addition of water decreases the specific gravity, 
while abstraction of fat increases it. It is possible, there- 
fore, by carrying out both methods of adulteration care- 
fully, to maintain the same gravity as in the original sam- 
ple, so that this datum alone will not suffice to detect 
adulteration. Taken in conjunction with either the figure 
for fat or for total solids, the specific gravity becomes of 



MILK ADULTERANTS. 43 

direct value, and furnishes a means for determining, by 
calculation, the remaining datum. 

Vieth has pointed out that in normal milks the following 
ratios obtain : Sugar : proteids : ash =13:9:2, and a 
determination of these ratios may aid in the attempt to 
distinguish genuine but abnormal milks from watered 
milks. In the case of a watered milk the proportion 
would remain unchanged, but in abnormal milk it has 
been found to vary. Richmond finds that " the most con- 
stant figure in normal milks is the proportion of ash to 
solids-not-fat, which averages 8.3 per cent, and very rarely 
passes outside of the limits of 8.0 per cent, and 8.5 per 
cent. In cases of low solids-not-fat this proportion has 
been disturbed, and the ash has had a higher ratio to the 
solids-not-fat. In no case has the percentage of ash in 
the milk fallen below 0.7 per cent., even in milks notably 
below the limit. In an adulterated milk containing, say, 
8 per cent, of solids-not-fat, the ash would usually be lower 
than this — about 0.66 per cent.; this difference is small, 
but as the ash is capable of being estimated with great ac- 
curacy, it is significant. Other observers have found the 
same thing." 

For milk control in dairies, etc., it will suffice to take 
the specific gravity by the lactodensimeter (see page 19) 
and the fat by the Leffmann-Beam method. From the 
figures thus obtained the total solids can be ascertained by 
Table B or Richmond's slide-rule. 

Various substances are added to milk to conceal adulter- 
ation or inferiority in quality. The most frequently em- 
ployed are coloring matters. Sugar, salt, and starch have 
been added to milk, but are of infrequent occurrence. It 
has been stated that chalk has been added, but this is ob- 



44 ANALYTIC PROCESSES. 

viously unlikely. The coloring matters most frequently 
employed are annatto and certain coal-tar colors. Cara- 
mel, saffron, and carotin are occasionally used. 

Annatto is easily detected by rendering the sample 
slightly alkaline by the addition of sodium acid carbonate, 
immersing in it a slip of filter paper, and allowing it to 
remain over night. The presence of annatto will be indi- 
cated by a distinct reddish-yellow tinge to the paper. 

Coal-tar colors are detected by adding to the milk 
ammonium hydroxid and allowing a piece of white wool 
to remain in it over night. The dye is taken up by the 
wool, which acquires a yellow tinge. When milk contains 
Martius' yellow, ammonium hydroxid intensifies the color 
and hydrochloric acid bleaches it. 

Further information as to coloring matters will be found 
under the analysis of butter. 

Starch may be detected by the blue color developed 
on the addition of solution of iodin to the milk, which 
has previously been heated to the boiling temperature and 
then cooled. Starch is very often added to ice-cream and 
similar articles. 

Salt and cane sugar are occasionally added to milk 
that has been diluted with water. The former is easily 
detected by the taste, the increased proportion of ash and 
of chlorin. Cane sugar may be detected, if in considera- 
ble quantity, by the taste. The quantitative determination 
is made by the methods described in connection with con- 
densed milk. 

Antiseptic substances are largely used, especially in the 
warmer season, as a substitute for refrigeration. Many of 
these are sold under proprietary names which give no indi- 



MILK ADULTERANTS. 45 

cation of their composition. Preparations of boric acid 
and borax were at one time the most frequent in use, but 
lately, formalin, a 40 per cent, solution of formaldehyde 
(methyl aldehyde), has come into favor. Sodium benzoate 
is now in common use as a preservative for cider, fruit- 
jellies, and similar articles, and may, therefore, be found 
in milk. Salicylic acid is not so much employed as in 
former years. Sodium carbonate is occasionally used to 
prevent coagulation due to slight souring. 

R. T. Thomson ("Glasgow City Anal. Rep., 1895," 
quoted in Analyst, March, 1896) has studied the compara- 
tive value of milk preservatives. He finds that a mixture of 
boric acid and borax is more efficient than the acid alone. 
The quantity generally used is equivalent to about one-half 
gram of boric acid per liter. Formalin was shown to be 
by far the most efficient antiseptic. In the proportion of 
0.125 gram to the liter, it kept milk sweet for eight days. 

Formaldehyde. — The presence of this body may 
sometimes be detected by its odor developed on warming 
the milk. Hehner's method, the most characteristic for 
its detection, depends upon the fact that when milk contain- 
ing it is mixed with sulfuric acid a blue color appears. 
Richmond and Bosely showed that the delicacy of the test 
is much increased by diluting the milk with an equal bulk 
of water and adding sulfuric acid of 90 to 94 per cent., so 
that it forms a layer underneath the milk. Under these 
conditions, milk, in the absence of formaldehyde, gives a 
slight greenish tinge at the junction of the two liquids, 
while a violet ring is formed when formaldehyde is present 
even in so small a quantity as one part in 200,000 of milk. 
The color is permanent for two or three days. In the ab- 
sence of formaldehyde, a brownish color is developed after 



46 ANALYTIC PROCESSES. 

some hours, not at the junction of the two liquids but 
lower down in the acid. 

Another test is by the use of SchifT's reagent — a solution 
of magenta bleached by sulfurous acid. In presence of 
an aldehyde a pink color is developed. This test is usu- 
ally applied to the distillate from the milk, but Richmond 
and Bosely consider it safe to use the whey produced by 
adding dilute sulfuric acid to the milk. They point out 
further that great care must be exercised in applying the 
test. Excess of sulfurous acid must be carefully avoided 
in preparing the reagent, since the color is not developed 
in its presence. On the other hand, a red color is easily 
developed in the reagent by warming, blowing air through 
it, or even placing it in an uncorked bottle. Hehner has 
shown that when a small amount of the reagent, say two 
drops, is added to the distillate from the milk, a red color, 
due to the oxidation of the sulfurous acid by the oxygen of 
the water, is developed after some time, whereas no color 
appears if a larger amount — say ten drops — has been added. 
He recommends to add about five drops of the reagent to 
the distillate (amounting to about 25 c.c.) from 100 c.c. 
of milk, place the mixture in a stoppered cylinder, observe 
the color next morning, and then add a few drops of sul- 
furous acid solution. After a short time, any color which 
may be due to oxidation will have vanished, while that due 
to the presence of an aldehyde remains. There is a differ- 
ence in the tint produced by color oxidation, which re- 
sembles that of rosanilin, and that of the aldehyde com- 
pound, which is violet ; and with the small amounts that 
are often to be detected, only a comparison of the relative 
colors would allow of anything like a safe conclusion being 
drawn. Hehner also recommends the following as a sensi- 



MILK ADULTERANTS. 47 

tive and characteristic test : To the distillate from the milk, 
add one drop of a dilute aqueous solution of phenol, pour 
the mixture upon strong sulfuric acid contained in a test- 
tube. A bright crimson zone appears at the line of contact. 
This color is readily seen with one part of formaldehyde in 
200,000 of water. If there is more than one part in 100,000, 
there is seen above the red ring a white, milky zone, while 
in stronger solutions a copious white or slightly pink, curdy 
precipitate is obtained. This reaction has an advantage 
over the one above referred to, in that it is obtained with 
formaldehyde solution of all strengths, while the blue color 
with sulfuric acid is not obtained with milk containing 
much formaldehyde. Acetaldehyde also gives a coloration 
and a precipitate with phenol and sulfuric acid, but it is 
orange-yellow, not crimson. 

Many hydroxy-derivatives of benzene, such as salicylic 
acid", resorcinol, and pyrogallol, give the red color with 
formaldehyde. Hydroquinone does not give the red color 
but only an orange-yellow one. 

The reaction only succeeds when carried out as described 
above ; the phenol must first be mixed with the solution to 
be tested, and the mixture poured upon the sulfuric acid. 
Only a trace of phenol must be used. If the hydroxy- 
compound is first dissolved in the acid and the formal- 
dehyde solution then added, no color is obtained. 

The precipitate obtained by sulfuric acid, formaldehyde, 
and phenol is highly insoluble, and might be utilized 
for the determination of the strength of dilute formalin 
solutions. 

Benzoates. — Two hundred and fifty to five hundred 
c. c. of the sample are rendered alkaline by a few drops of 
calcium or barium hydroxid, evaporated to one-fourth bulk, 



48 ANALYTIC PROCESSES. 

mixed with sufficient calcium sulfate, powdered pumice, or 
other inert material as an absorbent, to make a pasty mass, 
and dried on the water bath. When condensed milk is 
examined, ioo to 150 grams should be mixed directly with 
sufficient absorbent material and a few drops of barium 
hydroxid. The dry mass is finely powdered, moistened 
with dilute sulfuric acid, and then exhausted three or four 
times with about twice its volume of cold (50 per cent.) 
alcohol, which dissolves benzoic acid freely, but only mere 
traces of the fat. The alcoholic liquid which, in addition 
to the benzoic acid, contains milk-sugar and mineral mat- 
ter, is mixed thoroughly, neutralized with barium hydroxid, 
and evaporated to small volume. The residue is acidified 
with weak sulfuric acid and extracted with successive small 
portions of ether. On evaporation, the ether leaves, almost 
pure, the benzoic acid, which may be recognized by its 
odor and volatility. 

Boric Acid. — When boric acid or borates are not pres- 
ent in quantities sufficient to appreciably increase the ash 
of the sample, the quantitative determination is difficult. 
The qualitative test is delicate. One hundred c. c. of 
the sample are rendered alkaline with calcium hydroxid, 
evaporated and ashed. Calcium hydroxid is preferred 
because the ashing takes place more rapidly. The ash is 
dissolved in the smallest possible quantity of strong hydro- 
chloric acid, the solution filtered, and evaporated to dryness. 
An appreciable loss of boric acid will not occur. The 
residue is moistened with very dilute hydrochloric acid, 
mixed with tincture of turmeric, and dried on the water bath. 
The smallest trace of boric acid gives to the residue a ver- 
milion or cherry-red tint. 

Concentrated hydrochloric acid gives, with tincture of 



MILK ADULTERANTS. 49 

turmeric, a cherry-red color, which, however, disappears on 
addition of water, and also becomes brown on drying, while 
the boric acid color appears only on drying, and is not 
destroyed unless much water be added, or at the boiling 
point. The red color adheres strongly to the vessel, and 
may be removed by alcohol. The flame test may be applied 
to the residue, but it is not delicate. 

R. T. Thomson (Analyst, March, 1896) gives the fol- 
lowing method for the estimation of boric acid. One 
hundred c. c. of milk are mixed with from one to two 
grams of sodium hydroxid, evaporated to dryness in a 
platinum dish, the residue thoroughly charred, heated with 
20 c. c. of water, and hydrochloric acid added drop by 
drop until all but the carbon is dissolved. The bulk should 
not be allowed to exceed 60 c.c. The liquid is trans-- 
ferred to a 100 c. c. flask, 0.5 gram of dry calcium chlorid, 
a fe\v drops of phenolphthalein solution added, then a 
10 per cent, solution of sodium hydroxid until a permanent 
pink color is produced, and then 25 c. c. of lime-water. 
All the phosphate will be thus precipitated as calcium phos- 
phate. The mixture is made up to 100 c. c, well mixed, 
and 50 c. c. collected through a dry filter. Normal sul- 
furic acid is added to this until the pink color is discharged, 
then methyl orange is added and the acid again dropped 
until the yellow tinge is just changed to pink. Fifth-nor- 
mal sodium hydroxid is added (with care to avoid ex- 
cess) until the liquid is yellow. At this stage all acids 
likely to be present exist as salts, neutral to phenolphtha- 
lein, except boric acid (which, being neutral to methyl 
orange, is in the free condition) and a small amount of 
carbonic acid that may be expelled by a few minutes' boil- 
ing. The solution is cooled, a little phenolphthalein added, 



5° 



ANALYTIC PROCESSES. 



and as much glycerol as will give at least 30 per cent, of 
that substance in the solution, and then titrated with fifth- 
normal sodium hydroxid until the pink color appears. 
Each c. c. of the alkaline solution equals 0.0124 of crys- 
tallized boric acid. The process is satisfactory with milks 
containing not over 0.2 per cent, of boric acid. The 
charring must be carried only so far as to obtain a residue 
which will give a clear solution with the hydrochloric acid. 
Boric acid may also be estimated by Gooch's method 
which is described in the analytic manuals. Hehner 
{Analyst, 1891) has modified the method by substituting 
sodium phosphate for powdered lime. (See page 52.) 

Salicylic Acid. — Fifty c. c. of the sample are treated 
'with acid mercuric nitrate for the removal of the fat and 
proteids, as described in connection with the determina- 
tion of milk sugar, and the liquid filtered. The filtrate is 
shaken violently with about one-half its volume of a mix- 
ture of equal parts of ether and petroleum ether. The 
ethereal liquid is evaporated and a drop of neutral solution 
of ferric chlorid added to the residue. If salicylic acid 
be present, a characteristic violet color is developed. The 
reaction is very delicate. 

Sodium Carbonate. — The following method, due to 
E. Schmidt, is stated to be capable of detecting one-tenth 
of one per cent, of sodium carbonate, or of sodium acid 
carbonate. 

Ten c. c. of the milk are mixed with an equal volume 
of alcohol, and a few drops of a one per cent, solution of 
rosolic acid added. Pure milk shows merely a brownish- 
yellow color, but in the presence of sodium carbonate a 



MILK ADULTERANTS. 5 I 

more or less marked rose-red appears. The delicacy of 
the test is enhanced by making a comparison cylinder with 
the same amount of milk known to be pure. If the salt 
is present in considerable amount, it may be detected by 
the increase in the ash, its marked alkalinity and efferves- 
cence with acid. 

Preservation of milk samples. — For preserving milk sam- 
ples for future analysis or comparison, various substances 
have been suggested, among which are hydrofluoric acid, 
alcohol, chloroform, carbon disulfid and formaldehyde. 
Richmond reported {Analyst, 1889, p. 2) good results by 
the addition of 0.5 per cent, of commercial hydrofluoric 
acid. In a discussion at a meeting of the Society of Public 
Analysts, in October, 1894 {Analyst, 1894, p. 247), Allen" 
stated that he had added to each sample twice its weight of 
alcohol, but was not satisfied with this method, although it 
had, in some instances, served a good purpose. Mr. Rich- 
mond stated that he had been using formalin for a year and a 
half; 0.05 per cent, will keep milk for a month and larger 
quantities for an indefinite period. 

Be van has, however, noted the fact {Analyst, 1895, P- 
152) that the total solids of milk containing formaldehyde 
are always higher, and that the increase is much greater 
than can be accounted for, even assuming that the whole 
of the formaldehyde remains in the residue, which is im- 
probable, since it is volatile. Experiments on pure solu- 
tions of albumin, milk-sugar, and cane-sugar showed in 
each case an increase in residue when evaporated with 
formaldehyde. He has suggested that a small part, at 
least, of the increase in weight observed, is due to the 
formation of a non-volatile polymer of formaldehyde, and 



52 ANALYTIC PROCESSES. 

in the case of milk-residues the increase is largely due to 
the conversion of milk-sugar into galactose. 

Commercial solutions of formaldehyde, even after recent 
re-distillation, leave considerable residue, — probably the 
polymer, paraformaldehyde, — when evaporated in a flat 
dish in the manner employed in determining milk-solids. 

Addendum to detection of boric acid. — E. A. Farrington 
{J. A. C. S., Sept., 1896) has found that " preservaline " 
(which contains boric acid) added to fresh milk, increases 
the acidity four times as much as when added to water in 
the same proportion. He considers, therefore, that a milk 
which exhibits an acidity equal to 0.36 per cent, of lactic 
acid (8 c. c. of decinormal alkali to 20 c. c. of milk), and 
does not smell nor taste sour, has been probably adulterated 
with boric acid, since that proportion of lactic acid would 
be distinctly evident to the senses. 



DATA FOR MILK INSPECTION. 

VARIATIONS IN COMPOSITION. 

Average Proportion of Solids in Milk. — The 
most extensive data on this point are those obtained by 
Vieth, a summary of whose results, covering a period of 
eleven years, was published in the Analyst of May, 1892. 
The total number of samples was 120,540, and although 
some changes had been made in the methods of analysis 
since the beginning of the work, the results were recalcu- 
lated so as to be strictly comparable. The averages of the 
entire series were as follows : — 

Fat, 4.1 per cent. 

Non-fatty Solids, 8.S " 

Total Solids, 12.9 " 

Seasonal Variations in the Composition of 
Milk. — The diagrammatic synopsis of Vieth's results 
{Analyst, 1892) shows that a notable variation in the 
proportion of ingredients occurs during the year. The 
poorest quality occurs during the first half of the year, 
especially in April. A low figure is also frequently noted 
about July. In autumn the quality rises, being highest in 
October and November. 

The figures show that the variations in the total solids 
are due mainly to the variations in fat, but not entirely, 
for an increase in the proportion of fat is usually attended 
by a slight increase in the non-fatty solids. 
53 



54 DATA FOR MILK INSPECTION. 

The earlier tendency was to assign too high a limit for 
the non-fatty solids, since this figure was obtained by 
methods which failed to extract all the fat. In applying, 
therefore, the more modern processes, normal milk will 
be found to yield a figure for the non-fatty solids decidedly 
below the extreme limit of 9.5 per cent. Even nine per 
cent, for the non-fatty solids is more than is usually 
present. 

While it may be permissible in special cases, such as the 
purchase of milk under contract, or in the operation of a 
large dairy, to reject samples which yield below nine per 
cent, of non-fatty solids, it is not just to exact such a 
standard for purposes of public inspection, and as a basis 
for penal proceedings. The standard of the Society of 
Public Analysts of England (8.5 per cent, of non-fatty 
solids) has been found satisfactory in the large experience 
of the members of that body, and Dr. Vieth has ex- 
pressed himself as follows concerning it : 

" My object is by no means to raise the cry that the 
standard adopted by the Society is too high ; on the con- 
trary, I think it is very judiciously fixed, but in upholding 
the standard of purity it should not be forgotten that the 
cows have never been asked for, nor given their assent to 
it, and that they will at times produce milk below standard. 
A bad season for hay-making is, in my experience, almost 
invariably followed by a particularly low depression in the 
quality of milk, toward the end of winter. Should the 
winter be of unusual severity and length, the depression 
will be still more marked. Long spells of cold and wet, as 
well as of heat and drought, during the time when cows 
are kept on pasture, also unfavorably influence the quality 
and, I may add, quantity of milk." 



VARIATIONS IN COMPOSITION. 



55 



Deficient Solids. — The following are some instances 
of deficiency of solids in milk known to be genuine : — 

Sp. Gr. Fat S-A r -F. Total Solids Analyst 

1029.6 3.38 7.95 n-33 C. B. Cochran 

1030.0 3.62 8.31 11.93 

1029.3 3.63 8.02 11.65 

. . . 3.99 836 12.35 Leffmann and Beam 

... 3. 1 1 8.33 n-44 ") Monthly Averages 

... 305 8.33 11.38 £ N. J. State Agric'l 

. . . 3.23 8.44 11.67 ) Exp. Station 

The following analyses have been kindly furnished us 
by C. B. Cochran, in advance of publication by him. The 
samples were taken under precautions which ensured their 
genuineness. The data are all direct determinations. The 
total solids were obtained by drying in the usual manner, 
and the fat by the L-B. method. Low milks have been 
often noted in the vicinity of Philadelphia. 



Cow 


Sp. Gr. 


Fat 


S-NF. 


Total Solids 


Pansy, . 


. . 1026.6 


2-35 


6.78 


9-*3 


Rosie, . 


. . 1028.8 


2-95 


7-56 


10.51 


Dubell, . 


. . 1028.8 


2.40 


7-56 


9.96 


Gussie, . 


• • io 33-5 


2.90 


8.68 


11.58 



R. Bodmer {Analyst, 18 



5) reported the analysis of a 
sample obtained from one cow (June 13, 1895) as follows : 

Sp. Gr. Fat Froteids Sugar Ash 

1024.8 3.14 3-77 2.59 0.88 

In a herd of 60 cows, Richmond found 19 per cent, of 
the samples to contain between 8.38 and 8.50 per cent, 
solids-not-fat. 

The following instances of unusually rich milk, were 
reported in the Analyst, January, 1893 : — 



56 



DATA FOR MILK INSPECTION. 



Sp. Gr. 


Total Solids 


Fat 


Ash 


Analyst 


1026.6 


19.50 


11.06 


•53 


Smetham 


1027.8 


16.06 


7-37 


•te 


" 


IQ 3i-5 


14.98 


3-9 2 


— 


De Hailes 



Since a partial creaming takes place in the udder, the 
first milkings (fore-milk) are poorer, and the last milkings 
(strippings) richer in fat, than the average milk. To insure 
a proper sample, the entire milking must be taken. 

Babcock (Proc. 12th Annual Conv. A. O. A. C.,.p. 123) 
states that during the protracted drought of the summer of 
1895, tae average of nearly 100 determinations at the Uni- 
versity of Wisconsin creamery gave but a trifle over 8.5 
per cent, solids-not-fat. The casein was low in this milk, 
while the sugar was about normal in amount. Similar con- 
ditions have been observed by Van Slyke at the New York 
Station. 

Variation According to Breed. — The following fig- 
ures, taken from Bulletin 77 (1890), New Jersey State 
Agricultural Experiment Station, show the average com- 
position of milk of various breeds of cattle : — 

AVERAGE COMPOSITION OF MILK FOR EIGHT MONTHS. 



Herd 


Specific 
Gravity 




Perceni 


AGE 






Water 


Total 
Solids 


Fat 


Casein 

3-48 
3-92 
3.28 
3-90 

3-27 


Sugar 

4.84 
4.80 
4.69 
4-85 
4.80 


Ash 


Ayrshire, . . . 
Guernsey, .... 

Holstein-Friesian, 

Jersey, 

Short- Horn, . . . 


I034 I 
I035.O 

IO32.8 
IQ35-3 
1033- 9 


87.30 

S5-52 
87.88 
85.66 

87-55 


12.70 

I4.4S 
12.12 

14-34 
12-45 


3.68 
5.02 

3-5i 
4.78 
3-65 


O.69 

0-75 

O.64 

O.J5 
0.73 



VARIATIONS IN COMPOSITION. 



57 



Variations According to Season. — The following 
table is condensed from the above report : — 



HoLSTEIN- 

Friesian 



Jersey 



Guernsey ; Sh't-Horn 



Total „ . Total „. Total' r . 
Solids , Fat Solids Fat Solids Fat 



Total 
Solids 



Total 1 - . Total 
Solids * at Solids 



March, 
April, 
.May, . 
June, . 

July, • 

August, . , 
September 
October, 



13-00 3-95 I2 -46 3 
13.093.8512.393 
12.973.5412.573 
12.583.42,12.993 
12.723.71 11.443. 
13. oS 4.07 11.383, 
11.85 3.26 n.67 3. 

112.27 3.6o,I2.o8 2 



S9I4 


995 


36 


15. 


8414 


83 5 


32 


14 


•65 


I 5 


67 4 


30 


14 


■73 


n 


42 4 


08 


13 


11 


13 


464 


13 


13 


05 


13 


60 4 


22 


13 


•23 


15 


00 5 


oi> 


14 


•55 


15 


75 5 


71 


15 



295-46 13.994.69 

95 5.20 12.76 3. 89 
004.57 12.05 3.24 
864.55 11. 973. 23 
85 4.54 11. 89 3.28 
93 4.81 12.08 3.56 
67 5.22 12.243.47 
285.78 12.61S3.82 



Milk Standards. — Many efforts have been made to 
establish a minimum for the composition of normal milk, 
with a view to prevent adulteration. Standards proposed 
some years back, requiring a high proportion of non-fatty 
solids, were based upon analyses by methods which fail to 
extract the whole of the fat from the milk residue. The 
Society of Public Analysts of England formerly used a 
standard of nine per cent, non-fatty solids and 2.5 per 
cent, fat, but when the improved method of analysis was 
adopted, altered the standard to the figures given in the 
table. The following are some of the standards which 
have been adopted : — 



58 



DATA FOR MILK INSPECTION. 





Percentage b 


y Weights of Solids 


State, City, Etc. 


Non- 
fatty 


Fat 


Total 


Pennsylvania, 1885, 

New York, 1884, 

New Jersey, 1882, ...... 

Massachusetts, 1S86, 

Minnesota, 1889, 

Columbus, Ohio, . 

Baltimore, Md., 


9-5° 
9.OO 
9.OO 
9-30 

9-50 

9-375 


3.OO 
3.OO 
3.OO 
3-70 

3-50 

3- 125 


I2.50 
I2.00 
I2.00 
I3.OO 
May and June 12.00 
13.00 
12.50 
12.00 


Denver, Col., 






12.00 


Lansing, Mich., 




3.00 
3.00 
3-5° 
3-5o 


12.50 


Madison, Wis., 






Burlington, Yt., .... 




12.50 






12.00 


Portland, Oregon, 


Omaha, Nebraska, 

U. S. Treasury Department, . . 
Philadelphia, 1890, Ordinance, . 
Society of Public Analysts, . . . 


9-5o 
8.50 
8.50 


3.00 
3-5o 

3.00 


12.00 
13.00 
12.00 
11.50 



SANITARY RELATIONS. 

Several practical points of comparatively recent devel- 
opment are intimately connected with the work of the 
milk-analyst and need some discussion. It is now well 
recognized that the dairy is an important factor in the dis- 
tribution of disease, the influence taking place through 
several channels. 

Dairy-cattle are subject to several virulent infectious 
diseases which are communicable to man. The most im- 
portant of these is tuberculosis. The tendency at the pres- 
ent time is to the view that the keeping of dairy-cattle is 
a fruitful cause of the spread of this disease. The specific 
germ of tuberculosis may be conveyed both in meat and 



SANITARY RELATIONS. 59 

milk, and since the infection of the animal is not always 
recognized promptly, a most insidious source of danger 
exists. Other infectious and dangerous diseases, eg., scarlet 
fever, diphtheria, and typhoid fever, may be conveyed by 
milk. 

The common methods of adulterating milk, namely, by 
abstracting fat or adding water, diminish the food-value, 
but there has been great exaggeration of the importance of 
these changes. It can scarcely be sound to declare, as has 
occasionally been done by those engaged in promoting 
sanitary legislation, that milk reduced in fat by legitimate 
processes, or even watered to a considerable extent, is un- 
wholesome. It is occasionally stated that the digestion of 
the proteids of milk is dependent on the presence of a 
certain amount of fat, but the experimental or clinical 
evidence of this is, apparently, not precise. Several com- 
petent authorities, e. g., Vieth, UrTelmann, and Hartshorne, 
have unhesitatingly declared even closely-skimmed milk to 
be wholesome. As regards watered milk, it would be pre- 
posterous to assert that an article which is wholesome when 
containing nine per cent, of non-fatty solids, becomes un- 
wholesome when containing eight per cent. 

Efforts have been made in some localities to interfere 
with the sale of closely-skimmed milk, especially that ob- 
tained by the centrifugal method. The low fat-content is 
the only point in which this differs appreciably in compo- 
sition from ordinary milk. Since the proteids, sugar, and 
mineral matters are still in normal amount, skim-milk must 
have much food value. Questions of a broader character 
are, however, to be considered. Grotenfeldt (" Modern 
Dairy Practice," English Edition, trans, by F. W. Woll) 
discusses the matter at length and shows that the sepa- 



60 DATA FOR MILK INSPECTION. 

rator skim-milk, as compared with that obtained by the 
setting process, is purer and fresher. It has fewer bacteria 
than the milk from which it was prepared, and has been 
freed from the disagreeable and disgusting adventitious mat- 
ters that are so often present in whole milk. Concerning 
the objection to the low fat-content upon which is sometimes 
based a claim for a distinction between " skimmed milk " 
and "separator-milk," applying the former term to milk 
treated by the setting process, it must be noted that all 
but a very small amount of the fat may be removed by 
allowing the milk to stand for several days at a low tem- 
perature. 

The unwholesomeness of milk arises not from change in 
the proportions of its principal ingredients, but from con- 
tamination with microorganisms. The danger from cer- 
tain specific organisms has been mentioned, but the more 
frequent danger is from the ordinary non-pathogenic or 
putrefactive microbes, which, unless special care be taken, 
are invariably present and multiply rapidly. To prevent 
such conditions, resort is had to sterilization by heat. Brief 
exposure to a temperature of ioo° C. is sufficient in most 
cases, but if the milk be subsequently exposed to air at 
ordinary temperatures, or mixed with unboiled water, it 
will be again contaminated and undergo putrefactive 
changes. In the warmer seasons of the year, these changes 
occur with great rapidity. Since clinical experience seems 
to show that boiled milk is frequently an unsatisfactory 
food for infants, methods of fractional sterilization at lower 
temperatures have been suggested. These depend on the 
fact, that, while spores and immature microbes require a 
rather high temperature for their destruction, fully devel- 
oped organisms are more easily killed. By heating the 



SANITARY RELATIONS. 6 1 

milk, therefore, to a temperature much below the boiling 
point, the adult microbes are killed, while the milk-solids 
are not unfavorably affected. The spores and immature 
organisms will, however, survive and may in a few hours 
develop ; hence the milk is again heated, as before, and 
these later developed organisms will be killed. This pro- 
cess is repeated several times and finally complete steriliza- 
tion is effected. 

For the practical purpose of rendering milk safe as an 
article of food, it is not necessary to make repeated heat- 
ings. Numerous investigations are reported on this point, 
one of the more recent being a paper by Dr. R. G. Free- 
man {Med. Rec, June 10, 1893). A temperature of 167 
F. (75 ° C.) continued for fifteen minutes, followed by 
rapid cooling by immersing the containing vessel in water, 
will kill the adult forms of most microbes, and milk so 
treated will remain unaltered for one or two days and will 
not have suffered any appreciable loss of digestibility, even 
for infants. 

When it is considered that milk is almost the only form 
of animal food that is eaten in the uncooked condition, by 
civilized communities, the importance of the facts above 
noted will be apparent. Some interesting data as to the 
association of consumption, diphtheria, and similar dis- 
eases with the maintenance of dairies have been collected, 
but the discussion of this feature of the question would be 
out of place here. Enough is known to show that raw 
milk is not a safe article of food, unless collected with 
such precautions as will prevent the introduction of infec- 
tious matter. 

Artificial coloring matters do not involve any serious 
danger to health, except Martius' yellow (dinitroalpha- 



62 DATA FOR MILK INSPECTION. 

naphthol) which is poisonous. The obvious objection to 
their use is that they enable milk of inferior quality to be 
substituted for rich milk. It is worthy of note that the 
assertion, occasionally made, that urine is employed in the 
preparation of annatto, is of little weight, since the an- 
natto sold for dairy use is prepared by unobjectionable 
methods. 

Abnormal Milks.— Milk occasionally becomes blue 
on the surface, the color forming in patches in proportion 
as the cream rises. The condition is due to the develop- 
ment of a chromogenic bacillus, first noted by Ehrenberg, 
and by him called Vibrio syncyanus, but now more cor- 
rectly called Bacillus syncyanus. The condition some- 
times prevails in epidemic form. The butter prepared 
from such milk possesses a greenish color, and a disagree- 
able butyric odor. The bacillus seems to be non-patho- 
genic. Hueppe fed animals on food mixed with strong 
cultures of it, and observed no serious results. To pre- 
vent the development and spread of the bacillus it is 
recommended that the vessels intended to receive the 
milk be washed in boiling water. Reiset states that blue 
milk may be used for the production of butter by adding 
0.5 gram of acetic acid to each liter (eight grains to the 
quart). 

Red milk is due to accidental contamination with the 
Bacillus prodigiosus. The spores of this microbe exist in 
the atmosphere and rapidly develop when they fall upon 
any nutritive medium. The microbe does not appear to 
have any pathogenic properties. 

Ropy Milk. — This condition is occasionally seen dur- 



SANITARY RELATIONS. 6$ 

ing moist warm weather. The milk when drawn may not' 
show any unusual properties, but in a few hours becomes 
so viscid that a spoonful of it may be lifted several inches 
without breaking the connection between the two portions. 
The nature and cause of the change are not known. The 
phenomenon generally appears rather suddenly and does 
not last long, almost always disappearing promptly on the 
advent of colder weather. Cases are known in which the 
milk thus affected has been used as food without any 
apparent unfavorable effect. 



MILK PRODUCTS. 

CONDENSED MILK. 

A few brands of condensed milk in the market under 
the name of "evaporated cream," consist merely of 
whole milk concentrated to about two-fifths of its bulk, 
but most condensed milks contain a considerable amount 
of cane-sugar. These samples represent, usually, whole 
milk concentrated to about one-third or two-sevenths of 
its original volume. A small amount of invert-sugar may 
be present. Portions of the lactose may crystallize from 
condensed milk, and when solutions are prepared for 
analysis, abnormal polarimetric reading will result unless 
the liquid stands a considerable time or is heated for a 
short time to ioo° C. 

The analysis of unsweetened condensed milks is con- 
ducted as with ordinary milk, the sample having been 
previously diluted with several times its weight of water 
heated to boiling, cooled and made up to a definite 
volume. The fat may be readily estimated in unsweetened 
milks by the L-B. process, but in sweetened ones, the 
charring action of the sulfuric acid seriously interferes. 
We find that mixing 5 c. c. of diluted condensed milk 
with 3 c. c. of the hydrochloric-fusel-oil mixture in the 
test-bottle, filling up to the neck with glacial acetic acid 
and heating for a few minutes in boiling water will avoid 
charring and allow the fat to be brought up by the centri- 



CONDENSED MILK. 65 

fugal machine, but we have not tested the method suffi- 
ciently to ascertain its accuracy. 

The most common defect in condensed milks is de- 
ficiency in fat, due to preparation from closely-skimmed 
milks. English analysts have frequently called attention 
to such samples, but the reports of analysts in the United 
States indicate that such practices are uncommon in this 
country. We have from time to time examined very cheap 
samples of condensed milk sold in Philadelphia, but have 
not found any marked deficiency in fat. Attention has 
been called, especially by Allen, to the fact that labels on 
condensed-milk tins often advise such large additions of 
water as to produce a weak milk. Preservatives (other than 
cane-sugar) and coloring matters are rarely if ever used, 
nor is it likely that foreign fats will be present. 

The presence of cane-sugar, and possibly of invert- 
sugar, renders the complete analysis of condensed milk 
rather tedious, but for many practical purposes it will be 
sufficient to determine the total solids, fat, and proteids. 
If the ash and milk-sugar also be determined, the cane- 
sugar may be approximately estimated by difference. In 
all examinations of condensed milk, care should be taken 
that the contents of the can are thoroughly mixed before 
any sample is taken. The following procedures cover the 
usual analysis of ordinary samples, and are partly those 
given by Pearmain and Moor. 

Ten grams of the sample should be dissolved in water 
and made up to ioo c. c. Aliquot portions of this solu- 
tion should be taken for analysis. 

Total Solids. — Five to ten c. c. are evaporated by 
the Babcock method (p. 21), or on ignited asbestos in 
a shallow platinum basin. 



66 MILK PRODUCTS. 

Ash. — Twenty c. c. or more are evaporated in a plati- 
num dish and the ash determined with the usual precau- 
tions. 

Fat. — The cylinder containing the residue from the 
determination of total solids is placed in the extractor and 
the fat obtained in the usual way. Another method is to 
distribute five c. c. over fat-free paper, proceeding as in the 
original Adams' process. The Werner-Schmidt method 
is not suitable. 

Proteids. — These determinations are made as with 
ordinary milk. 

Sugars. — If regard is to be had to the possible pres- 
ence of invert-sugar, a special method must be followed 
which is described below. The processes first given con- 
sider lactose and sucrose only. 

Lactose. — Richmond and Bosely have shown that heat- 
ing to the extent to which milk is subjected in the prepara- 
tion of condensed milk may reduce the rotatory power of 
the sugar sufficiently to cause serious error, if the polari- 
meter be used for the determination. The reducing power 
with alkaline copper solutions is not seriously affected. 

Sucrose. — The determination of cane-sugar may be made 
by difference, that is subtracting the sum of the other ingre- 
dients from the total solids. Such a method is, of course, 
approximate only, but it may serve for ordinary inspection 
purposes, since the amount present is almost always large, 
generally more than the milk-solids themselves, and an 
error even of several per cent, does not affect the judg- 
ment as to the wholesomeness of the sample. More exact 
work requires, however, that the cane-sugar shall be 
determined directly, and several processes have been 
devised for the purpose. Sucrose exerts but little action 



CONDENSED MILK. 67 

on Fehling's solution, but invert-sugar acts powerfully, and 
one set of processes depends on determining the reducing 
power before and after inversion. Since the polarimetric 
reading is also markedly changed by the inversion, the 
difference in polarization may be employed. Processes of 
fermentation maybe so conducted as to remove the sucrose 
(also any form of glucose) while the lactose is unaffected. 
This method is chiefly valuable for recognizing invert- 
sugar or either of its constituents. 

When inversion methods are used, they must be such as 
to secure prompt inversion of the sucrose without affecting 
the lactose. Experiment shows that citric acid and inver- 
tase (the enzyme of yeast) are the most suitable agents. 
Stokes and Bodmer {Analyst, 1885, P- 62) have worked out 
the citric acid method substantially as follows : — 

About eight grams of the sample are accurately weighed, 
diluted with water, coagulated with about one per cent, of 
citric acid, without heating, and made up to 200 c. c. plus 
the volume of the precipitated fat and proteids (see p. 39). 
The liquid portion, which now measures 200 c. c, is passed 
through a dry filter. The reducing power with alkaline 
copper solutions is determined at once upon 50 c. c. of this 
filtrate. To another 50 c. c, one per cent, of citric acid 
is added and the solution boiled for ten minutes and the 
reducing power also determined. The increase over that 
of the first solution is due to the invert-sugar formed by 
the action of the citric acid on the sucrose. It is neces- 
sary to bear in mind that the reducing equivalents of lac- 
tose and invert-sugar are not the same. Stokes and Bod- 
mer prefer to work with Pavy's solution. The following 
description is partly from their paper and partly from 
Allen's " Chemistry of Urine." 



68 MILK PRODUCTS. 

Pavy's solution : — 

Pure crystallized copper sulfate, . . . 4. 157 grams 
Pure crystallized Rochelle salt, . . .21.6 grams 
Sodium hydroxid of good quality, . .20.5 grams 

The copper sulfate is dissolved in about 100 c. c. of hot 
water, the Rochelle salt and sodium hydroxid are dissolved 
in another portion of warm water, the solutions allowed to 
cool and mixed, 400 c. c. of ammonium hydroxid (sp. gr. 
.880) added and the liquid made up to one liter. 

Of this solution, 

10 c. c. equals 0.005 dextrose 

10 c. c. equals 0.0096 lactose 

10 c. c. equals 0.0047 sucrose (after inversion). 

The best results are obtained only when working so as to 
exclude free access of air. Allen suggests the following 
arrangement : To the lower end of the buret is attached a 
short rubber tube which connects with a glass tube that 
passes through a rubber stopper fitted in a flask of conveni- 
ent size. The stopper has two other openings, one for the 
admission of a tube through which a slow current of illum- 
inating gas or hydrogen may be transmitted in order to 
maintain a non-oxidizing atmosphere ; the other for a tube 
for the escape of steam and ammonium hydroxid. 

The gas connection may be omitted if, as suggested by 
Stokes, the tubes through which the vapors escape be joined 
with an empty WoolfFs bottle connected by a tube to a ves- 
sel containing cold water. The flask containing the copper 
solution may be placed upon a whitewashed iron plate in 
order to show the tint of the solution more clearly. 

From 25 to 40 c. c. of the copper solution, accurately 
measured, are placed in the flask, a few fragments of pum- 
ice dropped in, the tubes and buret adjusted, and the solu- 



CONDENSED MILK. 



tion brought to boiling. The liquid containing the lactose 
is added in small portions. Since the oxidizing action 
occurs more slowly than with glucose, the additions must be 
at greater intervals. The process is finished as soon as the 




From Allen's "Chemistry of Urine." 



liquid is colorless. When common coal gas flows into the 

flask, a brick-red film of cuprous acetylid is formed on the 

surface of the liquid from the acetylene present in the gas. 

It is necessary to verify the correctness of the copper 



70 MILK PRODUCTS. 

solution and this may be done by means of known weights 
of pure lactose and sucrose, the latter being first inverted 
by the citric acid as described. 

Allen has recently {Analyst, 1895, P- I2 7) stated that 
the Gerrard-Allen method — titration with cupric cyanid — 
promises to be the most satisfactory volumetric method for 
glucose and that it may answer also for other sugars. It is 
described in full in Pharmaceutical Journal for April 20, 
1895, also in the "Chem. of Urine," above cited, p. 74. 

The following method is based on the difference in polari- 
metric reading before and after action of invertase. About 
30 grams of the sample are accurately weighed in a 100 
c. c. flask, diluted to about 80 c. c, heated to boiling, 
cooled, and 7.5 c. c. of acid mercuric nitrate solution 
added. The mixture is made up to 100 c. c, well shaken, 
filtered through a dry filter and the polarimetric reading 
taken at once. It will be the sum of the effect of the two 
sugars. The volume of the sugar-containing liquid is cal- 
culated by allowing for the precipitated proteids and fat, 
as described on p. 39. 

Fifty c. c. of the filtrate are placed in a flask marked at 
55 c. c, a piece of litmus paper dropped in, and the excess 
of nitric acid cautiously neutralized by sodium hydroxid 
solution. The liquid is then faintly acidified by a single 
drop of acetic acid (it must not be alkaline), a few drops 
of an alcoholic solution of thymol added, and then 2 c. c. 
of a solution of invertase, prepared by grinding half a 
cake of ordinary compressed yeast with 10 c. c. of water 
and filtering. The flask is corked and allowed to remain 
at a temperature of 35 to 40 C. for twenty-four hours. 
The cane-sugar will be inverted while the milk-sugar will 



CONDENSED MILK. 7 I 

be unaffected. The flask is filled to the mark (55 c. c.) 
with washed aluminum hydroxid and water, mixed, fil- 
tered, and the polarimetric reading taken. 

A powerful solution of invertase may be prepared by 
the method recommended by O' Sullivan and Tompson. 
Brewer's yeast is allowed to stand at a temperature of 
1 5 C. for a month. The liquid is filtered and sufficient 
alcohol added to give about 12 per cent, of absolute 
alcohol. After a few days the liquid is filtered and is 
ready for use. The alcohol acts as a preservative. 

The rotatory powers of cane-sugar and dextrose are not 
appreciably affected by temperature within the limits of 
ordinary experiments. The same may be said of milk- 
sugar (see p. 41). Invert-sugar, by reason of the levu- 
lose present, is materially affected by the temperature. 
Thus, a solution of cane-sugar, which, before inversion, 
causes a rotation of -j- 100 angular degrees, has after 
inversion, if observed at o° C, a rotation of — 44 degrees, 
a total change of 144; but at 21 C. the reading will 
be only — 33 angular degrees, a total change of 133. 
The following formula is to be used for calculation : — 

c = JooD 



t 

144 

2 

in which C equals the angular rotation due to the unin- 
verted cane-sugar, D the difference in the polarimetric 
reading before and after inversion, and t the temperature 
in Centigrade degrees. Since in the performance of the 
inversion, the liquid has been diluted from 50 to 55 c. c, 
the polarimetric reading must be increased in proportion, 
before the value of D is found. 



72 MILK PRODUCTS. 

The specific rotatory power of cane-sugar varies slightly 
with the concentration. Tollens gives the following 
formula, in which S is the specific rotatory power and C 
the concentration in grams per ioo c. c. : — 

S = 66.386 -f- .015035 C— .0003986 C 2 

Bigelow and McElroy (y. A. C. S., Dec, 1893) propose 
the following routine method for the determination of the 
sugars, including invert-sugar, in condensed milk. The so- 
lutions used are : — 

Acid mercuric iodid. — Mercuric chlorid, 13.5 grams; 
potassium iodid, 33.2 grams; glacial acetic acid, 20 c.c. ; 
water 640 c.c. 

Alumina- cream. — A cold saturated aqueous solution of 
alum is divided into two unequal portions; to the larger 
portion ammonium hydroxid is added to slight excess, and 
then small portions of the remaining solution until a slight 
acid reaction is secured. 

The entire contents of the can are transferred to a porce- 
lain dish and thoroughly mixed. A number of portions 
of about 25 grams are weighed carefully in 100 c.c. flasks. 
Water is added to two of the portions, and the solutions 
boiled. The flasks are then cooled, clarified by means of 
a small amount of the acid mercuric iodid and alumina- 
cream, made up to mark, filtered and the polarimetric 
reading noted. Other portions of the milk are heated in 
the water-bath to 55 C. ; one-half of a cake of com- 
pressed yeast is added to each flask and the temperature 
maintained at 55 C. for five hours. Acid mercuric iodid 
and alumina-cream are then added, the solution cooled to 
room-temperature, made up to mark, mixed, filtered, 
polarized. The amount of cane-sugar is determined by 






CONDENSED MILK. 73 

formula on page 71. Correction for the volume of 
precipitated solids may be made by the double dilution 
method (p. 41). The total reducing sugar is estimated in 
one of the portions by one of the reducing methods, and 
if the sum of it and the amount of cane-sugar obtained 
by inversion is equal to that obtained by the direct reading 
of both sugars before inversion, no invert-sugar is present. 
If the amount of reducing sugar seems to be too great, the 
milk-sugar must be re-determined as follows : Two hundred 
and fifty grams of the condensed milk are dissolved in 
water, the solution boiled, cooled to 8o° C, a solution of 
about four grams of glacial phosphoric acid added, the 
mixture kept at 8o° C. for a few minutes, then cooled to 
room temperature, made up to mark, shaken and filtered. 
It may be assumed that the volume of the precipitate is 
equal to that obtained by mercuric iodid solution. Enough 
potassium hydroxid is then added to not quite neutralize 
the free acid, and sufficient water to make up for the volume 
of the solids precipitated by the phosphoric acid. The 
mixture is then filtered and the filtrate is measured in por- 
tion of 100 c.c. into 200 c.c. flasks. A solution containing 
20 milligrams of potassium fluorid and half a cake of com- 
pressed yeast is added to each flask, and the mixture al- 
lowed to stand for ten days at a temperature of from 25 ° 
C. to 30 C. The invert-sugar and cane-sugar are fer- 
mented and removed by the yeast in the presence of a 
fluorid, while milk-sugar is unaffected. The flasks are filled 
to the mark and the milk-sugar determined either by reduc- 
tion or by the polariscope. The amount of copper solution 
reduced by the lactose and invert-sugar, less the equivalent 
of lactose remaining after fermentation, is due to invert- 
sugar. 

b' 



74 



MILK PRODUCTS. 





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75 



BUTTER. 

Butter, commercially, consists of a variable mixture of 
fat, water, and curd, obtained by churning cream from cow's 
milk. The water contains in solution milk-sugar and the 
salts of the milk. Common salt is usually present, being 
added after the churning. Artificial coloring is frequently 
used. 

The composition of commercial butter usually varies 
within the following limits : — 

Fat, 78 per cent, to 94 per cent. 

Curd, 1 " " " 3 " " 

Water, 5 " " " 14 " " 

Salt, o " " " 7 " " 

Nostrums for Butter Making. — Preparations are 
sold .purporting to have the power to increase the yield of 
butter from a given weight of milk. One of these, adver- 
tised under the name "black pepsin," has been found to 
contain salt, annatto, and a small amount of rennet. Pep- 
sin has also been used. These curdle the milk and allow 
the incorporation of much cheese and water with the but- 
ter. Butter may also, without the addition of chemicals, 
be incorporated with a large amount of cream. 

We have encountered butter containing over forty per 
cent, of water. Such samples are pale and spongy, lose 
weight, and become rancid very rapidly. 

It is generally considered that butter should not con- 
tain more than 16 per cent, water. An excess of water 
diminishes the keeping quality. 

The following methods for the analysis of butter have 
been adopted by the A. O. A. C. : — 



J 6 MILK PRODUCTS. 

Sampling. — If large quantities of butter are to be sam- 
pled, a butter trier or sampler may be used. The por- 
tions drawn, about 500 grams, are to be carefully melted 
in a closed vessel, at as low a heat as possible, and when 
melted the whole is to be shaken violently for some minutes 
till homogeneous. The mass must be sufficiently solidified 
to prevent the separation of the water and fat. A portion 
is then placed in the vessel from which it is to be weighed 
for analysis, and should nearly or quite fill it. It should 
be kept in a cold place until analyzed. Determinations 
are made as follows : — 

"Water. — 1.5-2.5 grams are dried to constant weight at 
the temperature of boiling water in a dish with a flat bot- 
tom, having a surface of at least 20 sq. cm. The use of 
clean, dry sand is admissible. 

Fat. — The dry butter from the water determination is 
dissolved in the dish with absolute ether, or with 76 
petroleum spirit. The contents of the dish are then trans- 
ferred to a Gooch crucible with the aid of a wash-bottle 
filled with the solvent, and are washed until free from fat. 
The crucible and contents are dried at the temperature 
of boiling water, until the weight is constant. 

Indirect Method. — Water may be determined by dry- 
ing on asbestos or sand, and the fat extracted by ether. 

Casein and Ash. — The crucible containing the res- 
idue from the fat determination, consisting of the casein 
and salts, is covered and heated, gently at first, and grad- 
ually raising the temperature to just below redness. The 
cover may then be removed and the heat continued till 
the contents of the crucible are white. The loss in weight 
of the crucible and contents represents the weight of the 
casein, and the residue in the crucible, ash. The mineral 
matter may be dissolved in water very slightly acidulated 
with nitric acid, and the chlorin determined in the usual 
way. 

Salt. — Weigh in a counterpoised beaker from 5 to 10 
grams of the sample. The butter is placed, in portions 



BUTTER. 7 7 

of about i gram at a time, in the beaker, these portions 
being taken from different parts of the sample. Hot water 
is now added (about 20 c. c.) to the beaker containing the 
butter, and after it has melted the liquid is poured into 
the bulb of a separating funnel. The stopper is now in- 
serted and the contents shaken for a few moments. After 
standing until the fat has all collected on top of the water, 
the stopcock is opened and the water is allowed to run into 
an Erlenmeyer flask, being careful to let none of the fat 
globules pass. Hot water is again added to the beaker, 
and the foregoing process is repeated from ten to fifteen 
times, using each time 10 to 20 c c. of water. The result- 
ing washings contain all but a mere trace of the NaCl 
originally present in the butter. The sodium chlorid may 
be determined volumetrically in the nitrate. 

Antiseptic substances in milk may find their way 
into the butter made from it. They will be dissolved in 
the water, and may be detected by separating this, by melt- 
ing, and testing it as directed under milk. 

Oleomargarin. — Under this term is now included by 
act of Congress, any oleaginous substance intended as a 
substitute for butter, containing any proportion of fat 
other than butter-fat. The term "margarine" is em- 
ployed in England, under authority of an act of Parlia- 
ment, with the same significance. The principal materials 
employed in the preparation of butter substitutes are cot- 
tonseed oil, mutton-fat, and beef- fat. 

When fats are saponified and the soap treated with acid, 
the individual fatty acids are obtained. It is upon the 
recognition of the peculiar acid radicles existing in butter 
that the most satisfactory method of distinguishing it from 
other fats is based. Since the relative proportion of these 
radicles differs in different samples, the quantitive estima- 
tion cannot be made with accuracy, but when the foreign 



78 MILK PRODUCTS. 

fats are substituted to the extent of 25 per cent, or more, 
the adulteration can be detected with certainty and an 
approximate quantitive determination made. 

Distillation method. — The fatty acids containing a small 
number of carbon atoms, set free by the process noted 
above, are soluble in water and volatile. A method for 
their estimation depending on their solubility in water was 
perfected by Hehner, but has now been displaced by a dis- 
tillation method originally suggested by Hehner & Angell, 
but improved by Reichert, and the details perfected by 
others, especially Wollny, and now generally known as the 
Reichert-Wollny method. 

We have modified the process by substituting a solution 
of sodium hydroxid in glycerol as the saponifying agent, 
by which the time required is much shortened, the result 
subject to less variation, and the titration more exact. The 
following reagents are required. 

Glycerol-soda. — One hundred grams of pure sodium 
hydroxid are dissolved in 100 c. c. of distilled water, 
and allowed to stand until clear. Twenty c. c. of this 
solution are mixed with 180 c. c. of pure concentrated 
glycerol. The mixture can be conveniently kept in a 
capped bottle holding a 10 c. c. pipet, with a wide outlet. 

Sulfuric acid. — Twenty c. c. of pure concentrated sul- 
furic acid, made up with distilled water to 100 c. c. 

Barium hydroxid. — An approximately decinormal, ac- 
curately standardized, solution of barium hydroxid. 

Indicator. — An alcoholic solution of phenolphthalein. 

About 50 grams of the sample are placed in a beaker, and 
heated to a temperature of 50 to 6o° C, until the 
water and curd have settled to the bottom. The clear fat 
is then poured on a warm, dry plaited filter, and kept in a 



BUTTER. 79 

warm place until 25 or 30 c. c. have been collected. If 
the filtrate is not perfectly clear, it should be reheated for 
a short time and again filtered. 

A 300 c. c. flask is washed thoroughly, rinsed with alco- 
hol and then with ether, and thoroughly dried by heating 
in the water oven. After cooling it is allowed to stand 
for about fifteen minutes and weighed. A pipet, gradu- 




ated to 5.75 c. c. , is heated to about 6o° C. and filled to 
the mark with the well-mixed fat, which is then run into 
the flask. After standing for about fifteen minutes the 
flask and contents are weighed. Twenty c. c. of the gly- 
cerol-soda are added and the flask heated over the Bunsen 
burner. The mixture may foam somewhat ; this may be 
controlled, and the operation hastened by shaking the 
flask. When all the water has been driven off, the liquid 



80 MILK PRODUCTS. 

will cease to boil, and if the heat and agitation be con- 
tinued for a few moments, complete saponification will be 
effected, the mixture becoming perfectly clear. The whole 
operation, exclusive of weighing the fat, requires less than 
five minutes. The flask is then withdrawn from the heat 
and the soap dissolved in 135 c. c. of water. The first 
portions of water should be added drop by drop, and the 
flask shaken between each addition in order to avoid 
foaming. When the soap is dissolved, 5 c. c. of the 
dilute sulfuric acid are added, a piece of pumice dropped 
in, and the liquid distilled until no c. c. have been col- 
lected. The condensing tube should be of glass, and the 
distillation conducted at such a rate that the above amount 
of distillate is collected in thirty minutes. 

The distillate is usually clear; if not, it should be thor- 
oughly mixed, filtered through a dry filter, and 100 c. c. of 
the filtrate taken. To the distillate about 0.5 c; c. of the 
phenolphthalein solution are added, and the standard 
barium hydroxid run in from a buret until a red color is 
produced. If only 100 c. c. of the distillate have been 
used for the titration, the number of cubic centimeters of 
barium hydroxid should be increased by one-tenth. 

When it is intended merely to distinguish butter from 
oleomargarin, it will be sufficient to measure into the flask 
3 or 6 c. c. of the clear fat, and operate upon this directly. 

A blank experiment should be made to determine the 
amount of decinormal alkali required by the materials em- 
ployed. With a good quality of glycerol, this will not 
exceed 0.5 c. c. 

Butter (5 grams) yields a distillate requiring from 24 to 
34 c. c. of decinormal alkali. Several instances have been 
published in which genuine butter has given a figure as low 



BUTTER. 8 1 

as 22.5 c. c, but such results are uncommon. The mate- 
rials employed in the preparation of oleomargarin yield a 
distillate requiring less than 1 c. c. of alkali. Commercial 
oleomargarin is usually churned with milk in order to 
secure a butter flavor, and thus acquiring a small amount 
of butter-fat yields distillates capable of neutralizing from 
1 to 2 c. c. of alkali. 

That more uniform results may be obtained with the 
glycerol-soda method than with the use of alcohol has been 
clearly shown. W. Karsch, assistant in the Dairy Institute 
at Hameln, Germany {Chemiker-Zeitung, 1896, 62), has 
subjected the method to careful comparative examination 
and finds it to be more satisfactory than the Reichert- 
Wollny method. Dr. Vieth, Director of the Institute, has 
employed it for several years in the analytic work of the 
statjon . 

The method of determining the volatile acids of butter- 
fat, adopted by the A. O. A. C, is as follows : — 

Sodium hydroxid solution. — One hundred grams of sodium 
hydroxid are dissolved in 100 c. c. of pure water. It should 
be as free as possible from carbonates, and be preserved 
from contact with the air. 

Alcohol, of about 95 per cent., redistilled over sodium 
hydroxid. 

Acid. — Solution of sulfuric acid containing 25 c. c. of 
strongest acid in 1000 c. c. of water. 

Barium hydroxid. — An accurately standardized, approx- 
imately decinormal solution of barium hydroxid. 

Indicator. — One gram of phenolphthalein in 100 c. c. of 
alcohol. 

Saponification flasks, 250 to 300 c. c. capacity, of hard, 
well-annealed glass, capable of resisting the tension of 
alcohol vapor at ioo° C. 

A pipet, graduated to deliver 40 c. c. 



82 MILK PRODUCTS. 

Distilling apparatus. 

Buret. — An accurately calibrated buret, reading to 
tenths of a c. c. 

The butter or fat to be examined should be melted, and 
kept in a dry, warm place at about 6o° C. for two or three 
hours, until the water and curd have entirely settled 
out. The clear supernatant fat is poured off and filtered 
through dry filter paper, in a jacketed funnel containing 
boiling water. Should the filtered fat in a fused state not 
be perfectly clear, the treatment above mentioned must be 
repeated. 

The saponification flasks are prepared by having them 
thoroughly washed with water, alcohol, and ether, wiped 
perfectly dry on the outside, and heated for one hour at 
the temperature of boiling water. The flasks should then 
be placed in a tray by the side of the balance, and covered 
with a silk handkerchief until they are perfectly cool. 
They must not be wiped with a silk handkerchief within 
fifteen or twenty minutes of the time they are weighed. 
The weight of the flasks having been accurately determined, 
they are charged with the melted fat in the following 
way : — 

A pipet with a long stem, marked to deliver 5.75 c. c, 
is warmed to a temperature of about 50 C. The fat 
having been poured back and forth once or twice into a dry 
beaker in order to thoroughly mix it, is taken up in the 
pipet and the nozzle of the pipet carried to near the 
bottom of the flask, having been previously wiped to remove 
any adhering fat, and 5.75 c. c. of fat are allowed to flow 
into the flask. After the flasks have been charged in this 
way, they should be re-covered with a silk handkerchief 
and allowed to stand fifteen or twenty minutes, when they 
are again weighed. 

Ten c. c. of 95 per cent, alcohol are added to the fat in 
the flask, and then 2 c. c. of the sodium hydroxid solution ; 
a soft cork stopper is now inserted in the flask and tied 
down with a piece of twine. The saponification is then 
completed by placing the flask upon the water or steam 



BUTTER. 83 

bath. The flask, during the saponification, which should 
last one hour, should be gently rotated from time to time, 
being careful not to project the soap for any distance up its 
sides. At the end of an hour the flask, after having been 
cooled to near the room temperature, is opened. The 
stoppers having been laid loosely in the mouth of the flask, 
the alcohol is removed by dipping the flask into a steam 
bath. The steam should cover the whole of the flask except 
the neck. After the alcohol is nearly removed, frothing 
may be noticed in the soap, and to avoid any loss from this 
cause or any creeping of the soap up the sides of the flask, 
it should be removed from the bath and shaken to and fro 
until the frothing disappears. The last traces of alcohol 
vapor may be removed from the flask by waving it briskly, 
mouth down, to and fro. After the removal of the alcohol 
the soap should be dissolved by adding 100 c. c. of recently 
boiled distilled water, warming on the steam bath with 
occasional shaking, until solution of the soap is complete. 
When the soap solution has cooled to about 65 C, the 
fatty acids are separated by adding 40 c. c. of the dilute 
sulfuric acid solution mentioned above. The flask should 
now be re-stoppered as in the first instance, and the fatty 
acid emulsion melted by replacing the flask on the steam 
bath. According to the nature of the fat examined, the 
time required for the fusion of the fatty acid emulsions 
may vary from a few minutes to several hours. 

After the fatty acids are completely melted, which can 
be determined by their forming a transparent oily layer on 
the surface of the water, the flask is cooled to room tem- 
perature, and a few pieces of pumice stone added. The 
pumice stone is prepared by throwing it, at a white heat, 
into distilled water, and keeping it under water until used. 
The flask is now connected with a glass condenser, slowly 
heated with a naked flame, until ebullition begins, and then 
the distillation continued by regulating the flame in such 
a way as to collect 110 c. c. of the distillate in, as nearly 
as possible, thirty minutes. The distillate should be re- 
ceived in a flask accurately graduated at noc.c. 



84 MILK PRODUCTS. 

The no c. c. of distillate, after thorough mixing, are 
filtered through dry filter paper and collected in a flask 
marked at ioo c.c. One hundred c.c. of the filtered distil- 
late are poured" into a beaker holding from 200 to 250 c.c, 
0.5 c.c. of phenolphthalein solution added, and decinormal 
barium hydroxid run in until a red color is produced. The 
contents of the beaker are then returned to the measuring 
flask to remove any acid remaining therein, poured again 
into the beaker, and the titration continued until the red 
color produced remains apparently unchanged for two or 
three minutes. The number of cubic centimeters of deci- 
normal barium hydroxid required should be increased by 
one-tenth. 

Many other methods of detecting butter adulteration 
have been proposed. The distinction between butter and 
its substitutes is not so sharp as with the distillation method, 
but all are of more or less value and may aid in the detec- 
tion of adulteration in doubtful cases. 

Acetic acid reaction (Valenta's test). — This depends upon 
the behavior of butter and acetic acid, and is one of the 
most valuable of the simple tests. The strength of acid 
used may vary within certain limits, but it must always be 
standardized against a sample of pure butter-fat. 

Three c. c. of the melted fat are placed in a dry test- 
tube, an equal volume of acetic acid added, and the mixture 
heated until solution has taken place. It is then allowed 
to cool spontaneously, and the temperature at which the 
liquid begins to be turbid noted. 

Messrs. Chattaway, Pearmain, and Moor, as the result of 
a rather lengthy trial, prefer an acid of about 95.5 percent. 
With a weaker acid the test is less sensitive. They call at- 
tention to the fact that the presence of moisture in the fat 
is one of the most fruitful sources of error, and recom- 



BUTTER. 85 

mend filtration of the sample through dry filter paper 
before performing the test. They note further that undue 
heating of the sample, either at the time the test is being 
made, or previously, renders the determination unreliable. 
With the acid employed by them, the following figures were 
obtained expressed in Centigrade degrees : — 

Butter-fat (24 samples) — 

Highest, 39 

Lowest, 29 

Mean, 36 

Oleomargarin (5 samples) — 

Highest, 97 

Lowest, 94 

Mean, 95 

Cottonseed oil, various samples, 71 , 75 , 71 , 85 , 

86°, 88°, 8g° 

Peanut oil, 72 , 73 

Lard oil, 75 , 76 , 75 

Lard, 98 , 97 , 98 , 97 

Beef stearin, ioo° 

Lard stearin, ioo°. 

E. W. T. Jones {Analyst, 1894, p. 151) recommends the 
employment of a standard butter with which to standardize 
each fresh batch of acid, and dilution of the acid to such a 
point, that the turbidity temperature with this butter-fat is 
6o° C. In this way the results are comparable with those 
of previous tests. 

Oleomargarin gives temperatures from 95 to 106 C, 
and generally from ioo° to 102 C. 

Iodin number. — The common oils and fats are mixtures 
of ethers of the acetic and oleic series. The former are 
saturated and therefore form only substitution compounds, 



86 MILK PRODUCTS. 

but the latter readily form additive compounds with the 
members of the chlorin group, and by estimating the 
amount of the element taken up under definite conditions, 
a measure of the amount of unsaturated radicles present is 
obtained. 

Hiibl's method with iodin is now employed. The A. 
O. A. C. process is as follows : — 

(i) Iodin solution. — Dissolve 25 grams of pure iodin in 
500 c. c. of 95 per cent, alcohol. Dissolve 30 grams of 
mercuric chlorid in 500 c.c. of 95 per cent, alcohol. 
The latter solution, if necessary, is filtered, and then the two 
solutions mixed. The mixed solution should be allowed 
to stand twelve hours before using. 

(2) Decinormal sodium thiosulfate solution. — Take 24.6 
grams of chemically pure sodium thiosulfate freshly pulver- 
ized as finely as possible and dried between filter or blotting 
paper. Make this up to 1000 c. c. at the temperature at 
which the titrations are to be made. 

(3) Starch paste. — One gram of starch is boiled in 200 c. 
c. of distilled water for ten minutes, and cooled to room 
temperature. 

(4) Solution of potassium iodid. — One hundred and fifty 
grams of potassium iodid are dissolved in water and made 
up to 1 liter. 

(5) Solution of potassium dichromate. — Dissolve 3.874 
grams of chemically pure potassium dichromate in distilled 
water, and make the volume up to 1 liter at the temperatuie 
at which the titrations are to be made. 

Run 20 c. c. of the potassium dichromate solution, to 
which has been added 10 c. c. of the solution of potassium 
iodid, into a glass stoppered flask. Add to this 5 c. c. of 
strong hydrochloric acid. Allow the solution of sodium 
thiosulfate to flow slowly into the flask until the yellow 
color of the liquid has almost disappeared. Add a few 
drops of the starch-paste, and with constant shaking con- 
tinue to add the sodium thiosulfate solution until the blue 
color just disappears. The number of cubic centimeters 



BUTTER. 87 

of thiosulfate solution used, multiplied by 5, is equivalent to 
1 gram of iodin. 

About 1 gram of butter-fat is to be weighed in a glass- 
stoppered flask holding about 300 c. c, with the precau- 
tions mentioned for weighing the fat for determining 
volatile acids. The fat in the flask is dissolved in 10 c. c. 
of chloroform. After complete solution has taken place, 
30 c. c. of the iodin solution are added. The flask is now 
placed in a dark place and allowed to stand, with occa- 
sional shaking, for three hours. 

One hundred c. c. of distilled water are added to the 
contents of the flask, together with 20 c. c. of the potas- 
sium iodid solution. Any iodin which may be noticed 
upon the stopper of the flask should be washed back into 
the flask with the potassium iodid solution. The excess of 
iodin is now taken up with the sodium thiosulfate solution, 
which is run in gradually, with constant shaking, until the 
yellow color of the solution has almost disappeared. A 
few drops of starch-paste are then added, and the titration 
continued until the blue color has entirely disappeared. 
Toward the end of the reaction the flask should be stop- 
pered and violently shaken, so that any iodin remaining in 
solution in the chloroform may be taken up by the potas- 
sium iodid solution in the water. A sufficient quantity of 
sodium thiosulfate solution should be added to prevent a 
reappearance of any blue color in the flask for five minutes. 

At the time of adding the iodin solution to the fats, two 
flasks of the same size as those used for the determi- 
nation should be employed for conducting the operation 
described above, but without the presence of any fat. In 
every other respect the performance of the blank experi- 
ments should be just as described. These blank experi- 
ments must be made each time the iodin solution is used. 



Example — Blank delerminatiotis. 

(1) 30 c. c. iodin solution required 46.4 c. c. sodium thio- 
sulfate solution. 



MILK PRODUCTS. 



(2) 30 c. c. iodin solution required 46.8 c. c. of sodium 

thiosulfate solution. 
Mean 46.6. 

Per cent, of iodin absorbed. 



1.0479 grams 
30.0 c. c. 
46.6 
14.7 
31.9 



Weight of fat taken, 

Quantity of iodin solution used, .... 
Thiosulfate equivalent to iodin used, . . 
Thiosulfate equivalent to remaining iodin, 
Thiosulfate equivalent to iodin absorbed, 

Per cent, of iodin absorbed, 31.9 X 0.0124 X 100 -f- 
1.0479=37.75. 

The iodin number for butter may range from 20 to 38 ; 
for oleomargarin from 40 to 55 ; the method is of little 
use, therefore, in this connection. 

Soluble and insoluble acids. — This method, originated 
by Hehner and Angell, has been improved by various 
chemists. Butter usually yields at least five per cent, of 
soluble and 89.5 of insoluble acids, but numbers slightly 
below these limits have been obtained in butters known to 
be pure. The following formula has been suggested for 
calculation of the amount of adulteration. F is the per- 
centage of foreign fat and I the percentage of insoluble 
acid : 

F=i 3 . 3 (I-88). 

The following are the reagents and manipulations pre- 
scribed by the A. O. A. C. :— 

Decinormal sodium hydroxid. 

Alcoholic potassa. — Dissolve 40 grams of good potassium 
hydroxid, free from carbonates, in one liter of 95 per cent, 
redistilled alcohol. The solution must be clear. 

Semi- normal hydrochloric acid accurately standardized. 

Indicator. — One gm. of phenolphthalein in 100 c. c. of 
alcohol. 



About 5 grams of the sample are weighed into a saponi- 
fication flask (p. 81), 50 c. c. of the alcoholic potassa solu- 
tion added, and the flask stoppered and placed in the 
steam bath until the fat is entirely saponified. The opera- 
tion may be facilitated by occasional agitation. The al- 
coholic solution is always measured with the same pipet, 
and uniformity further secured by allowing it to drain the 
same length of time (thirty seconds). Two or three blank 
experiments are conducted at the same time. In from five 
to thirty minutes, according to the nature of the fat, the 
liquid will appear perfectly homogeneous, saponification is 
complete, and the flask is removed and cooled. When 
sufficiently cool, the stopper is removed and the contents 
of the flask rinsed with a little 95 per cent, alcohol into 
an Erlenmeyer flask of about 200 c. c. capacity, which is 
placed on the steam bath, together with the blanks, until 
the alcohol is evaporated. Titrate the blanks with semi- 
normal hydrochloric acid. Then run into each of the 
flasks containing the fatty acids 1 c. c. more of the hy- 
drochloric acid than is required to neutralize the alkali 111 
the blanks. The flask is then connected with a condensing 
tube, three feet long, made of small glass tubing, heated 
on the steam bath until the separated fatty acids form a 
clear stratum. The flask and contents are then cooled in 
ice-water. 

The fatty acids having quite solidified, the liquid con- 
tents of the flask are poured through a dry filter into a 
liter flask, care being taken not to break the cake. 

Between 200 and 300 c. c. of water are next brought 
into the flask, the cork with its condenser-tube reinser- 
ted, and the flask heated on the steam bath until the 
cake of acids is thoroughly melted. During the melt- 
ing of the cake of fatty acids, the flask should occasion- 
ally be agitated with a revolving motion, but so that 
its contents are not made to touch the cork. When 
the fatty acids have again separated into an oily layer, 
the flask and its contents are cooled in ice-water and 
the liquid filtered through the same filter into the same 



90 MILK PRODUCTS. 

liter flask. This treatment with hot water, followed by 
cooling and filtration of the wash-water, is repeated three 
times, the washings being added to the first filtrate. The 
mixed washings and filtrate are next made up to i liter, 
and aliquot parts are titrated with the decinormal sodium 
hydroxid, and the total acidity calculated. The num- 
ber so obtained represents the volume of decinormal 
sodium hydroxid neutralized by the soluble acids of the 
butter-fat taken, plus that corresponding to the excess of 
the standard acid used, viz., i c. c. The number is, there- 
fore, to be diminished by 5, corresponding to the excess 
of 1 c. c. of semi-normal acid. This corrected volume, 
multiplied by .0088 gives the weight of butyric acid in 
the amount of butter-fat saponified. 

The flask containing the cake of insoluble acids and the 
paper through which the soluble acids were filtered are 
allowed to drain and dry for twelve hours, when the cake, 
together with as much of the acids as can be removed from 
the filter paper, are transferred to a weighed glass dish. 
The funnel and filter are then set in an Erlenmeyer flask, 
and the filter washed thoroughly with absolute alcohol. The 
flask is rinsed with the washings from the filter paper, then 
with pure alcohol, and these transferred to the glass dish, 
which is placed in the steam bath, and after the alcohol is 
evaporated the residue is dried for two hours in an air bath 
at ioo° C. , cooled in a desiccator, and weighed. It is heated 
in the air bath for two hours more, cooled and weighed. If 
the two weighings are decidedly different, a further heat- 
ing for two hours must be made. The residue is the total 
insoluble acids of the sample. 

Saponification equivalent {Koettstorfer number). This is 
the number of milligrams of potassium hydroxid required 
to saponify 1 gram of fat. The lower the molecular 
weight of the acid radicles present, the higher the Koetts- 
torfer number. The following is the A. O. A. C. process : — 

The reagents are the same as those employed in the de- 



BUTTER. 91 

termination of soluble and insoluble acid, except that the 
standard sodium hydroxid is not needed. 

Between one and two grams of the sample are weighed 
into a saponification flask (p. 81), 25 c. c. of the alcoholic 
potassium hydroxid added, the flask stoppered and heated 
in the steam bath until the fat is entirely saponified. The 
operation may be aided by occasional agitation. The al- 
kaline solution is to be always measured by the same pipet, 
and it should always be allowed to drain for the same length 
of time (thirty seconds). Several blank experiments should 
be conducted at the same time. 

As soon as the saponification is complete, the flasks are 
removed from the bath, cooled, and the contents titrated 
with semi-normal hydrochloric acid, using phenolphthalein 
as indicator. The Koettstorfer number is obtained by 
subtracting the number of cubic centimeters of hydro- 
chloric acid necessary to neutralize the alkali after saponi- 
fication, from the number necessary to neutralize the blank, 
multiplying the result by 28. 06, "and dividing the product 
by the number of grams of fat used. 

It is generally considered that a sample which gives a 
Koettstorfer number less than 226 is not pure butter-fat, and 
the formula proposed for calculating the probable amount 
of adulterant is x = 3.17 (227 — n) in which x is the per- 
centage of adulterant, and n the Koettstorfer number. 
With oleomargarin, beef dripping, tallow, and lard, usually 
n == 195 to 197. 

Various physical tests have been proposed, among which 
the most satisfactory are the viscosity and refraction index. 
Many observers have noted that a relation exists between 
the chemical composition of a liquid and the velocity of 
transpiration. 

Viscosity. — C. Killing (abstract in Analyst, 1895) uses 
the following apparatus for the determination of viscosity. 
A wide glass cylinder is closed at the bottom by a rubber 



92 MILK PRODUCTS. 

stopper, through which passes a short tube, having its top 
ground to receive a sort of pipet, which holds about 
50 c. c, and permits of the introduction of a small ther- 
mometer into the body. The upper tube of the pipet, 
which passes through the top stopper of the cylinder, is 
closed by a stopper. The pipet has three marks, one below 
the body and two above, the latter being placed about 
1 cm. apart. The stopper at the top of the cylinder is 
made in two pieces, and a second thermometer is passed 
through one of these. The whole apparatus is fixed in a 
clamp, and a beaker is placed below to receive the fat. 

Originally, the standard of viscosity was taken to be the 
time required for a definite volume of water at 20 C. to 
run out, but it was found that two apparatus might give 
identical results for water without doing so for some fat. 
The times will be similar only when the body of the 
pipet, delivery tube, etc., are exactly of the same dimen- 
sions. For this reason each apparatus must be standard- 
ized for the mean " running out " time of butter and for 
margarin. Killing gives the following average figures : — 

Butter, 3 min. 43.5 sec. 

Oleomargann, 4 " 19 " 

Lard, 4 " 28 " 

Beef- fat, 4 " ^^ " 

Except cocoa- fat, the viscosity of which is less than 
that of butter-fat, the values for vegetable fats used 
in oleomargarin are decidedly higher. Dr. Newman 
Wender (y. A. C. S., 1895, p. 719) has devised a form of 
apparatus called a Fluidometer. " The apparatus possesses, 
besides its inexpensiveness, other merits, chief among 
which is, that by means of a simple compression bulb, the 
liquid can be forced back and used for repeated determi- 
nations. The apparatus consists of a V-formed capillary 
tube, with both limbs enlarged and divided in such a man- 
ner that one arm holds 10 c. c. and the other 2 c. c. of 
the liquid. According to the laws of liquids in commu- 
nicating tubes, the liquid flows from the wide limb, through 
the capillary into the smaller limb, which is placed some- 



BUTTER. 93 

what lower. The viscosity is calculated from the time 
which is required for the liquid to flow from the first di- 
vision to the last upper division. There is no danger of 
error arising from the evaporation, or contamination with 
foreign substances in repeating the experiments, and, fur- 
thermore, the apparatus is easily and quickly cleaned. 
Since it has been demonstrated that the relation between 
molecular weight and viscosity is not affected by solvents, 
Wender uses in the fluidometer a solution of the melted 
fat in chloroform, in order to avoid the trouble of main- 
taining the fat in the melted condition. The viscosity of 
the solvent must be taken into account, in this case. The 
time of transmission of the solvent is set at ioo, and the 
calculations for solutions are based upon this." From a 
large number of results he gives the following figures : — 

Viscosity value for pure butter, 344.30 Time, 68.8 
" " " oleomargarin, 373.20 " 77.4 

'Every degree of temperature above 20 C. decreases the 
time of efflux by 1.45 seconds. A decreasing temperature 
retards the efflux by an average of 1.43 seconds for each 
degree. The results of these investigations show that the 
viscosimetric examination may yield as good service in 
distinguishing butter from oleomargarin, as any of the 
physical tests. 

Refractive index. — J. Skalweit has made determinations 
of the angle of refraction of various fats, and recommends 
its use in detecting butter adulteration. Abbe's refracto- 
meter was employed for the determination. 

The following are some of the results given : — 

Water, 1-333 

Genuine butter, 1.4652 

" 1-4658 

Lard, 1.4690 

Oleomargarin, 1st quality, ...... 1.4692 

" 2d " 1.4720 

3 d " t-479 6 

" oil, 1.4680 



94 MILK PRODUCTS. 

Butterin, 1.4712^1 

" 1.4693 I Hanoverian 

" 1.4698 I manufacture. 

1.4698 J 

" 1.4733 English make. 

An improvement on the Abbe instrument is the Oleo- 
refractometer of Amagat and Jean. With this, the difference 
between butter and its substitutes is much greater. For 
description of the instrument and results with various oils, 
see Muter, Analyst, 1890, and Pearmain, Analyst, 1895. 

Neither of the above instruments gives material aid in 
detecting additions of small percentages of foreign fat to 
butter. 

Me lti?ig point. — Genuine butter usually shows a melting 
point ranging from 32. 6° to 34.7 C. Lard gives figures 
between 42 and 43 C, and " oleo-oil " from 29 to 
30 C. Artificial butter may easily be prepared of the 
same melting point as pure butter. The determination of 
melting point is, therefore, of limited value in the detec- 
tion of butter adulteration. 

Specific gravity. — Skalweit has noted that the greatest 
difference between the specific gravity of butter-fat and 
its adulterations is found at a temperature of 35 . The 
temperature usually employed is that of boiling water, and 
the comparison is made with water at 15.5 C. as unity. 

The determination is conveniently made with the 
Sprengel tube, which is filled by inserting the wider end in 
the melted fat and exerting suction. It is then placed in 
boiling water in a beaker, so that the capillary ends pro- 
ject slightly above the surface of the water. When the fat 
has ceased to expand, the excess is removed from the 
orifice by means of filter paper, the tube withdrawn from 
the water, dried, allowed to cool, and weighed. The 



BUTTER. 95 

weight of fat divided by the weight of water contained 
by the tube at 15. 5 C. gives the specific gravity. 

The Westphal balance is also recommended by Estcourt 
for these determinations. The melted fat is contained in 
a wide test-tube immersed in boiling water, care being 
taken to protect the balance from the steam. 

The specific gravity of butter-fat determined in this 
way usually varies between .865 and .867, while that of 
oleomargarin varies between .856 and .860. 

Considerable use has been made of a method based 
upon the detection of crystalline structure by examination 
with polarized light. Such condition indicates, however, 
merely that the sample has been previously melted. By 
churning oleo-oil with cream, a material is obtained which 
shows no crystalline structure when examined in this way. 

'Commercial forms of oleomargarin and butter exhibit 
characteristic differences on heating, which may be utilized 
for rapidly sorting a collection of samples. When butter 
is heated in a small tin dish directly over a gas flame, it 
melts quietly, foams, and may run over the dish. Oleo- 
margarin, under the same conditions, sputters noisily as 
soon as heated and foams but little. Even mixtures of 
butter and other fats show this sputtering action to a con- 
siderable extent. The effect depends upon the condition 
in which the admixed water exists, and the test is not 
applicable to butter which has been melted and reworked. 

An alcoholic solution of sodium hydroxid, heated for a 
moment with butter, and then emptied into cold water, 
gives a distinct odor of pineapples (due to ethyl butyrate), 
while oleomargarin gives only the alcoholic odor. 

E. A. de Schweinitz and J. A. Emery (/. A. C. S., Feb., 
1896) have found that the heat of combustion of butter- 



g6 MILK PRODUCTS. 

fat differs notably from that of other fats. They regard 
the method as capable of detecting small amounts of 
adulteration. It requires a special form of calorimeter 
which is not described in the article. 

W. Arnold (quoted in Druggist s Circular, September, 
1896) states that butter-fat is less transparent to X-rays 
than many common fats, but the fact has not yet been 
applied in a practicable form for analytic work. 

Butter Colors. — Various vegetable colors have been 
used in butter, especially turmeric and annotto, which are 
still employed, but coal-tar colors are rapidly replacing 
them. One of the first of this class to be used was " butter- 
yellow" (dimethylamidoazobenzene), but latterly other 
azo-colors readily soluble in oils have been employed. 
Dairymen now use mostly proprietary preparations, but the 
composition of these articles is liable to change, without 
notice, as cheaper or more suitable colors are discovered. 
Those now generally in use can scarcely be regarded as 
dangerous to health, since apart from the fact that few 
coal-tar colors have appreciable toxic action, the quantity 
used in the butter is very small. The normal coloring 
matter of butter is not soluble in alcohol. 

The following test, described by E. W. Martin, we 
have found very satisfactory. Dissolve 2 parts of carbon 
disulfid in 15 parts of alcohol, by adding small portions of 
the disulfid to the alcohol and shaking gently ; 25 c. c. of 
this mixture are placed in a convenient tube, 5 grams of 
the butter-fat added, and the tube shaken. The disulfid 
falls to the bottom of the tube, carrying with it the fatty 
matter, while any artificial coloring matter remains in the 
alcohol. The separation takes place in from one to three 
minutes. If the amount of the coloring matter is small 



CHEESE. 97 

more of the fat may be used. If the alcoholic solution be 
evaporated to dryness and the residue treated with concen- 
trated sulfuric acid, annotto will be indicated by the pro- 
duction of a greenish-blue color. With many samples of 
oleomargarin a pink tint will be obtained which indicates 
a coal-tar color. 

CHEESE. 

Cheese is the curd of milk which has been separated 
from it, pressed, and undergone some fermentation. The 
precipitation is produced either by allowing the milk to 
become sour — when the lactic acid is the agent — or by 
rennet. The first named method is mainly applied to the 
manufacture of so-called Dutch or sour-milk cheese, green 
Swiss cheese, and cottage cheese. More commonly cheese 
is obtained by means of rennet derived from the fourth 
stomach of the calf. The action is due to a non-organized 
ferment (enzym) rennin, which acts directly on the pro- 
teids and does not produce its effect through the interven- 
tion of acids. (See p. n.) The curd (cheese) undergoes, 
by keeping, various decompositions, some essentially putre- 
factive, and due to the action of microbes. The decom- 
position of the cheese is termed "ripening." In the 
ripening of some cheeses, moulds as well as bacteria play 
an important part. Thus, in the manufacture of Roquefort 
cheese, mouldy bread is introduced between the layers of 
curd, and the surrounding atmosphere is kept moist to 
assist in the growth and development of the fungi. 

In the sour-milk cheeses, ripening is restricted intention- 
ally, since there is liability to an irregular and miscel- 
laneous bacterial growth by which the fermentations may 
be carried too far, undesirable and even harmful products 
being formed. Such cheeses are intended for immediate use. 



98 MILK PRODUCTS. 

Cheese contains no casein, if by this term is meant the 
proteid as it exists in milk, or when precipitated from 
milk by acids. When milk is coagulated by rennet, only 
a part of the casein is found in the curd ; and, whereas, 
true casein contains about 15.7 per cent, of nitrogen, the 
proteid matter of cheese contains about 14.3 per cent. 
Under the process of ripening this is further decomposed, 
amido- and ammonium compounds being formed, and 
possibly proteoses. The following figures, obtained by Van 
Slyke, will serve to give some idea of the extent to which 
the curd is changed in ripening. The figures represent 
average percentage on the total nitrogen. The cheese in 
question was an American cheddar. 

Green Cheese. After five months. 

Soluble nitrogen compounds, . .4.23 35.52 

" amido " . . None 11.66 

" ammonium " . . None 2.92 

Van Slyke's experiments seem also to indicate that the 
cheese ripened more rapidly when the curd was precipi- 
tated by a larger quantity of rennet and especially, that 
cheese rich in fat ripened more rapidly than skim-milk 
cheese. 

The extent and character of the decomposition of the 
curd varies greatly in the different varieties of cheese, the 
fermentative process in each case being carried on by a dif- 
ferent group of microorganisms. In the harder cheeses 
the decomposition is slower and less complete than in the 
softer ones, in which the fermentation process is of an in- 
tensely active character. Recent progress in the study 
of the bacteriology of cheese indicates that at no distant 
date it will be possible to control the quality of the article 



CHEESE. 99 

by inoculating the milk or curd with pure cultures of 
microorganisms. 

In addition to the fat and nitrogenous compounds just 
mentioned, cheese may contain a small amount of milk- 
sugar and of lactic and other organic acids. There is 
present also a certain proportion of mineral matter, alka- 
line and earthy phosphates, along with any salt that has 
been added. Traces of nitrates have been found. 

Skimmed milk is not infrequently used for the produc- 
tion of cheese. Foreign fats, such as are used in the 
manufacture of oleomargarin, are sometimes incorporated, 
the article being often known as " filled cheese." 

The analytic points usually determined in regard to 
cheese, are amounts of water, fat, casein, ash, the presence 
of fats other than butter-fat, and coloring matters. 

In addition to this, especially in comparing the qualities 
of genuine cheeses, the proportion of proteic, amidic, and 
ammoniacal nitrogen is of value. 

Care should be taken to select for analysis a sample 
which represents the average composition of the entire 
cheese. A thin section, reaching to the center, is prefer- 
able, and portions from various parts of this should be cut 
fine and mixed. This should be done with as little expo- 
sure to air as possible, to avoid loss of water. 

The following methods for water, fat, ash, and total 
nitrogen are provisionally adopted by the A. O. A. C: — 

Water. — From 5 to 10 grams of cheese should be 
taken and placed in thin slices in a weighed platinum or 
porcelain dish which contains a small quantity of freshly 
ignited asbestos, to absorb the fat which may run out of 
the cheese. The mass is then heated in a water oven for 
ten hours, and weighed ; the loss in weight is to be con- 
sidered as water. 



IOO MILK PRODUCTS. 

Ash. — The dry residue from the water determination 
may be taken for the ash. If the cheese be rich, the as- 
bestos will be saturated therewith. This mass may be 
ignited carefully, and the fat allowed to burn off, the as- 
bestos acting as a wick. No extra heating should be 
applied during the operation, as there is danger of spurt- 
ing. When the flame has died out, the burning may be 
completed in a muffle at low redness. When desired, the 
salt may be determined in the ash by titration with silver 
nitrate and potassium chromate. 

Fat (Ether extract). — Five to 10 grams of the sample 
are ground in a small mortar with about twice the weight 
of anhydrous copper sulfate. The grinding should be 
continued until the cheese is finely pulverized and evenly 
distributed throughout the mass, which will have a uniform 
blue color. This mixture is transferred to a glass tube 
which has strong filter paper, supported by a piece of mus- 
lin, tied over the end. A little of the clean anhydrous 
copper sulfate is put into the tube next to the filter before 
introducing the mixture containing the cheese. On top 
of the mixture is placed a tuft of ignited asbestos, and the 
contents of the tube extracted with anhydrous ether in 
the continuous extraction apparatus, for fifteen hours. The 
ether is removed as usual and the fat dried at 21 2° F., to a 
constant weight. (The fat-free thimbles noted in connec- 
tion with the description of the Adams process will proba- 
bly be found convenient substitutes for the glass tube and 
filter. The fat-free residue should be tested for starch.) 

Nitrogen. — The nitrogen of about two grams of the 
cheese is determined by the Kjeldahl-Gunning method. 

The above processes may be advantageously modified in 
some respects. The determination of water may be made 
by the extraction of the cheese with alcohol and ether and 
drying of the alcohol-ether extract and fat-free solids 
separately. Blyth recommends this method as more 
accurate and less tedious than the direct drying. In the 



determination of ash, it will be better to extract the 
charred mass with water and proceed as described in the 
determination of the ash of milk. 

The fat extracted by ether may be examined for other 
than butter-fat by the Reichert method in the usual way. 
When the composition of the fat is alone desired, it may 
often be extracted by simpler methods. Pearmain and 
Moor recommend that 50 grams be chopped fine and 
tied up in a muslin bag, which is placed in a water-bath. 
When the water is heated the fat will generally run out 
clear. If not clear it can be filtered through paper. 

O. Henzold (abstract in Analyst, 1895) suggests the 
following : Three hundred grams of the powdered cheese 
are agitated in a wide-neck flask with 700 c. c. of 5 per 
cent, solution of potassium hydroxid previously warmed to 
20° C. In about ten minutes the cheese dissolves, the fat 
floats, and by cautious shaking may be collected in lumps. 
The liquid is diluted, the fat removed, washed in very cold 
water, kneaded as dry as possible, melted, and filtered. It 
is claimed that the fat is not altered in composition by the 
process. 

The fat of cheese may be estimated by the centrifugal 
method, as follows : — 

About 3 grams of the mixed cheese are weighed and 
transferred to the bottle, the last portions being washed 
in with the aid of water. A few drops of ammonium 
hydroxid are added, and sufficient water to make the 
liquid about 15 c. c. The liquid is warmed with occa- 
sional shaking until the cheese is well disintegrated, and 
then treated as a sample of milk. The percentage of fat is 
found by multiplying the percentage reading by 15.45 and 
dividing by the number of grams of cheese taken for analysis. 



102 MILK PRODUCTS. 

Chattaway, Pearmain, and Moor use the following modi- 
fication : Two grams of the cheese are placed in a small 
dish and heated on the water-bath with 30 c. c. of con- 
centrated hydrochloric acid until a dark, purplish-colored 
solution is produced. The mixture is now poured into 
the test-bottle, portions of solution remaining in the dish 
rinsed with the hydrochloric acid fusel-oil mixture into the 
bottle, and, finally, enough strong hot acid added to fill 
the bottle up to the mark. It is then whirled for about a 
minute. 

Bondzynski (Analyst, abst.) applies the Werner-Schmid 
method to the determination of fat in cheese, as follows : 
A weighed quantity of the finely-shredded cheese is placed 
in the tube and decomposed with 20 c. c. hydrochloric 
acid of specific gravity 1.1, containing about 19 per cent. 
HC1. On cautiously warming over wire gauze, the melted 
fat rises to the surface. After cooling, 30 c. c. of ether 
are added and the tube warmed very gently until the acid 
and ethereal solution of fat separate sharply. Centrifugal 
force helps this, but is not essential. After the volume of 
ether has been read off, 20 c. c. are pipetted off into a 
weighed Erlenmeyer flask. From this the quantity of fat 
in the entire solution may be calculated. 

Determination of proteid nitrogen (Stutzer's method). — 
Place 0.7 to 0.8 gram of the cheese in a beaker, heat to 
boiling, add two or three c. c. of saturated alum solution 
(to decompose alkaline phosphate), add a quantity of copper 
hydroxid mixture prepared as below, containing about 0.5 
gram of the hydroxid, and stir thoroughly; filter when 
cold, wash with cold water, and without removing the 
precipitate from the filter determine the nitrogen by the 
Kjeldahl-Gunning method. Before distillation, sufficient 



CHEESE. 103 

potassium sulfid solution must be added to precipitate the 
copper. 

Copper hydroxid mixture. — Dissolve 20 grams of pure 
crystallized copper sulfate in one liter of water, and add 
five c. c. glycerol ; add dilute solution of sodium hydroxid 
until the solution is alkaline ; filter ; rub the preparation 
up with water containing five c. c. of glycerol per liter, 
and then wash by decantation or filtration until the wash- 
ings are no longer alkaline. Rub the preparation up again 
in a mortar with water containing ten per cent, glycerol, 
thus preparing a uniform gelatinous mass that may be 
measured with a pipette. Determine the quantity of cop- 
per hydroxid per centimeter of this mixture. 

Another method is to heat a portion of the cheese with 
water, precipitate the soluble proteids by lead acetate, and 
determine separately the nitrogen in the insoluble portion 
and lead acetate precipitate. 

Ammonium compounds. — About five grams of cheese are 
rubbed up in a mortar with water, transferred to a filter, 
and washed with a liter of cold water. The filtrate concen- 
trated by boiling (if alkaline, it must be neutralized before 
heating), magnesia added, the liquid distilled, and the am- 
monium hydroxid in the distillate estimated by titration 
with standard acid. 

Amido- compounds. — The nitrogen asamido-compounds is 
estimated by subtracting from the figurefor total nitrogen, 
the sum of the proteid and ammoniacal nitrogen. If 
nitrates are present, the nitrogen as such should also be 
estimated and subtracted. 

Chrome yellow has been found in the rind of cheese. It 
may be detected by ashing the sample in a porcelain cruci- 
ble, assisting the burning of the carbon by a little nitric 



io4 



MILK PRODUCTS. 



acid, and applying the usual tests for lead and chro- 
mium. 

ANALYSES OF VARIOUS CHEESES. 

(Reports by Chattaway, Pcarmain, and Moor.) 



Cheddar, . . 

Gorgonzola, . 

Dutch, . . . 

Gruyere, . . , 

Stilton, . . . 

Cheshire, . . 

Gloucester, . . 
Camembert, 

Parmesan, . . 

Roquefort, . . 
Double Cream, 

American, . . 











X 

< 


< 


33-o 


4-3 


29-5 


40.3 


5-3 


26.1 


41.8 


M 


IO.6 


28.2 


4-7 


28.6 


19.4 


2.6 


42.2 


37-* 


4.2 


3i-3 


33* 


5-o 


23-5 


47-9 


4.7 


41.9 


32.5 


6.2 


17. 1 


29.6 


6.7 


30.3 


57-b 


3-4 


39-3 


30.6 


3-0 


27.7 



24.2 

22.1 
27.O 
3O.O 
29.O 
31.6 
31-4 
3I.O 
28.O 
36.8 
31.2 
3-0 



431 

4-3 6 
5-ii 
4-93 

4-73 
4-03 
4.99 

3-83 
6.86 

4-45 
3-14 

4.84 



The last sample is " filled " cheese. 

Analyses of " Cacio-cavallo " (Horse-cheese, a very 
popular cheese in southern Italy), made from whole milk. 
(G. Sartori, Staz. Sper. Ag. ItaL, xxii, 337. Analyst, 
abstract, 1893) : — 

Water, 19. 756 

Fat, 36.706 

Total prutcids, 37-825 

Ash (without NaCl), 2.340 

Salt, 3.260 



Total, .... 

Pure proteids, . . . 
Amnion iacal nitrogen, 
Amidic nitrogen, . 
Reichert-Wollny figure for fa 



99.887 

34125 
.0616 
.665 

2 5-3° 



FERMENTED MILK PRODUCTS. 



I05 



FERMENTED MILK PRODUCTS. 

The usual fermentation of milk is the conversion of the 
lactose into lactic acid, but by special methods other 
changes may be substituted. These modified fermenta- 
tions are of rather ancient origin, and being produced by 
mixture of organisms, the products are complex and ir- 
regular. The proteids are more or less changed into pro- 
teoses and peptones. With advances in mycology, it will 
be possible to carry out each fermentation by a pure cul- 
ture and thus obtain a product of any desired compo- 
sition. 

Kumiss is milk which has undergone alcoholic fermen- 
tation. The inhabitants of the steppes of Russia prepare 
it from mare's milk. When cow's milk is used, cane- 
sugar must be added. It is often made by adding cane- 
sugar and yeast to skim-milk. 

Vieth {Analyst, 1885 and 1886) gives the following 
analyses of kumiss : — 



KUMISS FROM COW'S MILK. 















Q . 


3 




Ash. 




c 

X 


a 


H 


2 


z 




< 






At the End 






OF 



u 
J 
< 




CO 


fa 


< 

u 


< 


° s 

Sa 
< z 


< 

t-1 




a 

CO 


3 

"0 
co 


J3 

3 

C 


One day, 


I. 12 


H-33 


I.65 


2.06 


30 


•32 


.26 6.16 


.16 


.42 


One week, . 


.02 


8.93 


I.48 2.00 .22 


.56 


•97 3-14 


.22 


•34 


Three weeks, 


I.03 


8.66 


I.5S I.93 .21 


•74 


1.39 2.23 


•23 


•3S 


Three months 


I. 12 


8.52 


1.57 I.7O.O9 


.91 


1-94 i-73 
j 


•25 


•33 



The item " lactoproteid and peptone " refers to the sub- 

H 



106 MILK PRODUCTS. 

stances precipitated by tannin after removal of the casein 
and albumin. 

KUMISS FROM MARE'S MILK. 

At the Alcohol Fat Nitrogenous Lactic Sugar Ash 

end of Matters Acid 

I day, . . 2.47 1.08 2.25 0.64 2.21 0.36 

8 days, . . 2.70 1.13 2.00 1.16 0.69 0.37 

22 " . . 2 84 1.27 1.97 1.26 0.51 0.36 

Kefyr. — This is usually made from cow's milk. It has 
been used in the Caucasus for centuries. For its prepara- 
tion a peculiar ferment is used, which is contained in the 
kefyr grains. These are first soaked in water, by which 
they are caused to swell, and are rendered more active and 
then added to the milk. If taken out of the milk and 
dried, the grains may be used repeatedly. 

The following analysis is given by Hammarsten (quoted 
by Aikman, " Milk, Its Nature and Composition ") : — 

Alcohol, 0.72 

Fat, 3.08 

Casein, 2.94 

Albumin, 0.186 

Peptones, 0.067 

Lactose, 2.685 

Lactic Acid 727 

Ash, 708 

According to Konig, good kefyr will not contain more 
than one per cent, of lactic acid. 



APPENDIX. 



VIETH'S TABLE FOR CORRECTING THE SPE- 
CIFIC GRAVITY OF MILK FOR TEM- 
PERATURE, EXTENDED BY 
COCHRAN. 

The figures for temperatures from j8° to 45 inclusive, were determined 
by experiment by C. B. Cochran. 



DIRECTIONS FOR USE. 
Fihd the Temperature of the Milk in the uppermost horizontal line, 
and the Specific Gravity in the first vertical column. In the same 
line with the latter, under the Temperature, is given the Corrected 
Specific Gravity. 









Fa 


HRENHEIT DEGREES. 






Sp. Gr. 




















38 


39 


40 


41 


42 


43 


44 


45 


1027 


25.2 


25-3 


2 5-3 


25-4 


25-5 


25.6 


25-7 


2 S .8 


28 


26.1 


26.2 


26.2 


26.3 


26.4 


20.5 


26.6 


26.7 


29 


27.1 


27.2 


27.2 


27-3 


27.4 


27-5 


27.6 


27.7 


30 


28.0 


28.1 


28.I 


28.2 


28.3 


28.4 


28. s 


28.6 


3 1 


29.0 


29.1 


29.I 


29.2 


293 


29.4 


29-5 


29.5 


32 


29.9 


30.0 


30.O 


30.1 


30.1 


30.2 


30-3 


3°-4 


33 


30.7 


30-7 


3C 7 


30-9 


31.0 


3i 1 


31.2 


31-3 


34 


31-0 


3i-7 


31-7 


3i-9 


32.0 


32.1 


32.2 


32.2 


35 


3 2 -5 


32.6 


32-7 


32-9 


32-9 


33o 


33o 


33-o 


30 


33-5 


33-b 


33-7 


33-* 


33-9 


34o 


34.o 


34-0 


37 


34-5 


34-6 


34-7 


34-8 


34-9 


3.VO 


35-o 


35-o 


3« 


35-4 


35-5 


35-b 


35-7 


35-8 









107 



io8 



Sp. Gr. 


Fahrenheit Degrees. 
























46 


47 


48 


49 


5o 


5i 


52 


53 


54 


55 


I020 


I9.0 


19.1 


19.1 


19.2 


19.2 


19-3 


19.4 


19.4 


19-5 


19.6 


21 


20.0 


20.0 


20.1 


20.2 


20.2 


20.3 


20.3 


20-4 


20.5 


20.6 


22 


2I.O 


21.0 


21. 1 


21.2 


21.2 


21.3 


21.3 


21.4 


21.5 


21.6 


23 


22.o 


22.0 


22.1 


22.2 


22.2 


22.3 


22.3 


22.4 


22.5 


22.6 


24 


22.9 


23.0 


23.1 


23.2 


23.2 


23-3 


23-3 


23-4 


23-5 


23.6 


25 


23-9 


24.0 


24.0 


24.1 


24.1 


24.2 


24-3 


24.4 


24-5 


24.6 


26 


24.9 


24.9 


25.0 


25-1 


251 


25.2 


25.2 


25-3 


25-4 


25-5 


27 


25-9 


25-9 


26.0 


26.1 


26.1 


26.2 


26.2 


26.3 


26.4 


26.5 


28 


26.8 


26. S 


26.9 


27.0 


27.0 


27.1 


27.2 


27-3 


27.4 


27.5 


29 


27,8 


27.8 


27.9 


28.0 


28.0 


28.1 


28.2 


28.3 


28.4 


28.5 


30 


28.7 


28.7 


28.8 


28.9 


29.0 


29.1 


29.1 


29.2 


29-3 


29.4 


31 


29.6 


29.6 


29.7 


29.8 


29.9 


30.0 


30.1 


30.2 


30.3 


3°-4 


32 


30-5 


30.5 


30.6 


3°-7 


30-9 


31.0 


3ii 


31-2 


3i-3 


3i-4 


33 


31-4 


31-4 


3i-5 


3i-6 


3i-8 


3i-9 


32.0 


32.1 


32-3 


3 2 -4 


34 


32-3 


32-3 


32-4 


32-5 


32-7 


32-9 


33-0 


33-i 


33-2 


33-3 


35 


33-i 


33-2 


33-4 


33-5 


33-6 


33-8 


33-9 


34- 


34-2 


34-3 



TEMPERATURE CORRECTION. 



I09 



Sp. Gr. 


Fahrenheit Degrees. 
























56 


57 


58 


59 


60 


61 


62 


63 


64 


65 


1020 


19 


7 


19 


8 


19.9 


19.9 


20.0 


20.1 


20.2 


20.2 


20.3 


20.4 


21 


20 


7 


20 


8 


20.9 


20.9 


21.0 


21. 1 


21.2 


21.3 


21.4 


21.5 


22 


21 


7 


21 


8 


21.9 


21.9 


22.0 


22.1 


22.2 


22.3 


22.4 


22.5 


23 


22 


7 


22 


8 


22.8 


22.9 


23.0 


23.1 


23.2 


23-3 


23-4 


23-5 


24 


23 


6 


23 


7 


23.8 


23-9 


24.0 


24.1 


24.2 


24-3 


24.4 


24-5 


. 2 5 


24 


6 


24 


7 


24.8 


24.9 


25.0 


25-1 


25.2 


25-3 


25-4 


25-5 


26 


25 


6 


25 


7 


25.8 


25-9 


26.0 


26.1 


26.2 


26.3 


26.5 


26.6 


27 


26 


6 


26 


7 


26.8 


26.9 


27.0 


27.1 


27-3 


27.4 


27-5 


27.6 


28 


27 


6 


27 


7 


27.8 


27.9 


28.0 


28.1 


28.3 


28.4 


28.5 


28.6 


29 


28 


6 


28 


7 


28.8 


28.9 


29.0 


29.1 


29-3 


29.4 


29-5 


29.6 


30 


29 


6 


29 


7 


29.8 


29.9 


30.0 


30.1 


30-3 


30-4 


30-5 


30.7 


31 


30 


5 


30 


6 


30.8 


30-9 


31.0 


31.2 


3i-3 


3i-4 


3i-5 


3i-7 


32 


31 


5 


31 


6 


3i-7 


3i-9 


32.0 


32.2 


32.3 


32.5 


32.6 


32-7 


33 


32 


5 


32 


6 


32-7 


32-9 


33-o 


33- 2 33-3 


33-5 


33-6 33-S 


34 


33 


5 


33 


6 


33-7 


33-9 


34- 


34-2 


34-3 


34-5 


34.6(34.8 


35 


34 


5 


34 


6 


34-7 


34-9 


35>o 


35-2 


35-3 


35-5 


35-6 35-8 



Sp. Gr. 


Fahrenheit Degrees. 






















66 


67 


68 


69 


70 


7i 


72 


73 


74 


75 


I020 


20.5 


20.6 


20.7 


20.9 


21.0 


21. 1 


21.2 


21.3 21.5 


21.6 


21 


21.6 


21.7 


21.8 


22.0 


22.1 


22.2 


22.3 


22.4 


22.5 


22.6 


22 


22.6 


22.7 


22.8 


23.0 


23.1 


23.2 


23-3 


23-4 


23-5 


23-7 


23 


23.6 


23-7 


23.8 


24.0 


24.1 


24.2 


24-3 


24.4 


24.6 


24.7 


24 


24.6 


24.7 


24.9 


25.0 


25.1 


25.2 


25-3 


25-5 


25.6 


25-7 


25 


25.6 


25-7 


25-9 


26.0 


26.1 


26.2 


26.4 


26.5 


26.6 


26.8 


26 


26.7 


26.8 


27.0 


27.1 


27.2 


27-3 


27.4 


27-5 


27.7 


27.8 


27 


27.7 


27.8 


28.0 


28.1 


28.2 


28.3 


28.4 


28.6 


28.7 


28.9 


28 


28.7 


28.8 


29.0 


29.1 


29.2 


29.4 


29-5 


29.7 


29.8 


29.9 


29 


29.8 29.9 


30.1 


30.2 


30.3 


3°-4 


3o.5 


30-7 


30..9 


31.0 


30 


30.8 30.9 


3ii 


31.2 


3i-3 


31-5 


3i-6 


31-8 


31-9 


32.1 


3 1 


31. 8 32.0 


32.2 


32.2 


3 2 -4 


32.5 


32.6 


32.8 


33o 


33-i 


32 


32-9 33-o 


33-2 


33-3 


33-4 


33-6 


33-7 


33-9 


34° 


34-2 


33 


33-9 34-0 


34-2 


34-3 


34-5 


34-6 


34-7 


34-9 


35-i 


35-2 


34 


34-9 35-o 


35-2 


35-3 


35-5 


35-6 


35-8 


36.0 


36.1 


36.3 


35 


35-9,36.1 


36.2 


3 6 -4 


36.5 


36-7 


36.8 


37-o 


37-2 


37-3 



TOTAL SOLIDS CALCULATED. 



TOTAL SOLIDS CALCULATED FROM FAT AND 
SPECIFIC GRAVITY. 

Formula of Hehner and Richmond, corrected by H. Droop Richmond '. 
T. S. = - 4- - F + 0.14. 



1.0 1.1 1.2 

-|- 

1.0S 9.20 9 

■ 2I 9-33 

■33 9-45 

1.46 9.58 

.58 9.70 

.71 9.83 

1.83 9.95 
10.0S 10. 



1-4 



1030.5 


8.96 


9- 


31.0 


9.09 


9- 


•5 


9.21 


9- 


32.0 


9-34 


9- 


•5 


9.46 


9- 


33-o 


9-59 


9- 


■* 


9.71 


9- 


1034.0 


9. 84 


9- 



•3 2 


9- 


•45 


9- 


•57 


9- 


•7o 


9- 


.82 


9- 


•95 


10. 


•07 


10. 


>.20 


10. 



1.6 



1.8 



1.9 



44 9-5^ 9-68 9.80 9.92 10.04 
57 9.68 9.80 9.92 10.04 10.16 
69 9.81 9.93 10.05 10.17 10.29 

82 9.94 10.06 10.18 10.30 10.42 

I I 

94 10.06 10.1S 10.30 10.42 10.54 

07 IO. iq IO.31 IO.43 IO -55 IO.67 

■ I I J - 

19' 10.31 10.43 io.55 IO -°7 io-79 
vz 10.44 10.56 10.6S 10.S0 10.92 

II II 



APPENDIX. 



Sp. Gk. 


Fat 
























2.0 


2.1 


2.2 


2-3 


2.4 


2-5 




2.6 


2.7 


2.8 


2.9 


IO26.O 


9.04 


9.16 


9.28 


9.40 


9-52 


9.64 


9.76 


9.88 


10.00 


10.12 


•5 


9.17 


9.29 


9.41 


9-53 


9-65 


9-77 


9.89 


10.01 


10.13 


10.25 


27.0 


9.29 


9.41 


9-53 


9-65 


9-77 


9.89 


10.01 


10.13 


10.25 


10.37 


•5 


9.42 


9-54 


9.64 


9.76 


9.88 


10.00 


10.12 


10.24 


10.36 


10.48 


28.0 


9-54 


9.66 


9.78 


9.90 


10.02 


10.14 


10.26 


10.38 


10.50 


10.62 


•5 


9.67 


9-79 


9.91 


10.03 


10.15 


10.27 


10.39 


10.51 


10.63 


IO-75 


29.0 


9-79 


9.91 


10.03 


10.15 


10.27 


10.39 


10.51 


10.63 


10.75 


10.87 


•5 


9.92 


10.04 


10.16 


10.28 


10.40 


10.52 


10.64 


10.76 


10.88 


11.00 


30.0 


10.04 


10.16 


10.28 


10.40 


10.52 


10.64 


10.76 


10.88 


11.00 


11. 12 


• 5 io-i7 


10.29 


10.41 


io-53 


10.65 


10.77 


10.89 


11. 01 


11. 13 


11.25 


31.010.29 


10.41 


10.53 


10.65 


10.77 


10.89 


11. 01 


11. 13 


11.25 


n-37 


.5 10.42 


10.54 


10.66 


10.78 


10.90 


11.02 


11. 14 


11.26 


11.38 


11.50 


32.010.54 


10.66 


10.78 


10.90 


11.02 


11. 14 


11.26 


n.38 


11.50 


11.62 


.5 10.67 


10.79 


10.91 


11.03 


11. 15 


11.27 


n-39 


11.51 


11.63 


"•75 


33-o 


10.80 


10.92 


11.04 


11. 16 


11.28 


11.40 


11.52 


11.64 


11.76 


11.88 


•5 


10.92 


11.04 


11. 16 


11.28 


11.40 


11.52 


11.64 


11.76 


11.88 


12.00 


1034.0 


11.04 


11. 16 


11.28 11.40 


11.52 


11.64 


11.76 


11.88 


12.00 


12.12 



TOTAL SOLIDS CALCULATED. 



""3 



Sp. Gr. 


Fat. 
























3-o 


3-i 


3-2 


3-3 


3-4 


3-5 


3-6 


3-7 


3-8 


3-9 


IO26.O 


10.24 


10.36 


10.48 


10.60 


10.72 


10.84 


10.96 11.08 


11.20 11.32 


•5 


10.37 10.49 


10.61 


10.73 10.85 10.97 


n.09'11.21 


11.33. "-45 


27.0 


10.49 


10.61 


10.73 


10.85 10.97 11.09 


11. 21 11.33 


".45 "-57 


•5 


10.62 


10.74 


10.86 


10.98 


11. 10 


11.22 


11.34 11.46 


11.58 


11.70 


28.0 


10.74 


10.86 


10.98 


11. 10 


11.22 


U-34 


11.46 11.58 


11.70 


11.82 


•5 


10.87 


10.99 


11.11 


11.23 


H-35 


11.47 


11.59 11. 71 


11.83 


n-95 


,29.0 


10.99 


11. 11 


11.23 


n-35 


11.47 


n-59 


11.711k.83 


n-95 


12.07 


•5 


11. 11 


11.23 


H-35 


11.47 


n-59 


11. 71 


11.83 


"•95 


12.07 


12.19 


30.0 


11.24 


11.36 


11.48 


11.60 


11.72 


11.84 


11.96 


I2.08 


12.20 


12.32 


•5 


u-37 


11.49 


11. 61 


n-73 


11.85 


11.97 


12.09 


12.21 


12.33 


12.45 


31.0 


11.49 11. 61 


U-73 


11.85 


11.97 


12.09 


12.21 12.33 


12.45 


12.57 


•5 


11.62 


n-73 


11.85 


11.97 


12.09 


12.21 


12.33 


12-45 


12.57 


12.69 


32.0 


11.74 


11.86 


11.98 


12.10 


12.22 


12.34 


12.46 


12.58 


12.70 


12.82 


•5 


11.87 


11.99 


12. 11 


12.23 


12.35 


12.47 


12.59 


12.71 


12.8; 


12.95 


33-o 


11.99 


12. 11 12.23 


12.35 


12.47 


12.59 


12.71 


I2.83 


12.95 13.07 


•5 


12. 12 12.24 12.36 


12.48 


12.60 


12.72 


12.84 12.96 


13. oS 13.20 


1034.0 


12.24 12.36 12.48 


12.60 12.72 


12.84 


12.96 13.08 

1 


13.2013.32 



ii4 



APPENDIX. 





Fat. 


Sp. Gr. 
























4.0 


4.1 


4.2 


4-3 


4-4 


4-5 


4-6 


4-7 


4-8 


4.9 


I026.O 


II.44 


II.56 


11.68 


11.80 


11.92 


12.04 


12.16 


12.28 


12.40 


12.52 


•5 u-57 


II.69 


11.81 


U-93 


12.05 


12.17 


12.29 


12.41 


12.53 


12.65 


27.0 11.69 


II. 8l 


H-93 


12.05 


12.17 


12.29 


12.41 


12.53 


12.65 


12.77 


.5 11.82 


II.94 


12.06 


12.18 


12.30 


12.42 


12.54 


12.66 


12.78 


12.90 


28.0 11.94 


I2.o6 


12.18 


12.30 


12.42 


12.54 


12.66 


12.78 


12.90 


13.02 


.5 12.07 


12.19 


12.31 


12.43 


12.55 


12.67 


12.79 


12.91 


13-03 


13-15 


29.0 


I2.I9 12.31 


12.43 


12-55 


12.67 


12.79 


12.91 


1303 


13-15 


13-27 


•5 


12.32 12.44 


12.56 


12.68 


12.80 


12.92 


13-04 


13.16 


13-28 


13- 40 


30.0 


12.44 12.56 


12.68 


12.80 


12.92 


13.04 


13.16 


13.28 


13.40 


13-52 


•5 


12.57 12.69 


12.81 


12.93 


«3.o 5 


13-17 


13-29 


13-41 


13-53 


13-65 


31.0 


12.69 I2.8l 


12.93 


I3-05 


13-17 


13-29 


I3-4I 


13-53 


13-65 


13-77 


•5 


12.82 12.94 


13.06 


13.18 


I3-30 


13-42 


13-54 


13.66 


I3-78 


13.90 


32.0 


12.94 13.06 


13.18 


I3-30 


13.42 


13-54 


13.66 


13-78 


13.90 


14.02 


•5 


13.07 13.19 


I3-3I 


13-43 


13-55 


13.67 


13-79 


I3-9I 


14-03 


14-15 


33-o 


13-19 13-31 


13-43 


13-55 


13-67 


13-79 


I3-9I 


14.03 


14- 15 


14.27 


•5 


13.32 13.44 


13-56 


13.68 


13.80 


13.92 


14.04 


14.16 


14.28 


14.40 


1034.0 


13-44 I3-5 6 


13.68 


13.80 


13.92 


14.04 


14.16 


14.28 


14.40 


14-52 



TOTAL SOLIDS CALCULATED. 



Ir 5 



Sp. Gr. 


Fax. 
























5-o 


5-i 


5-2 


5-3 


5-4 


5-5 


5-6 


5-7 


5.8 


5-9 


IO26.O 


12 64 


12.76 


12 


88 


13.00 


13.12 


13 


24 


1 3 


36 


13 


48 


13.60 


13 


72 


•5 


12.77 


12.89 


13 


01 


13-13 


13-25 


13 


37 


13 


49 


13 


61 


13-73 


13 


85 


27.0 


I2.89 


13.01 


13 


13 


13-25 


13-37 


13 


49 


13 


61 


13 


73 


13-85 


13 


97 


•5 


I3.02 


13-13 


x 3 


25 


13-37 


*3-49 


13 


61 


13 


73 


I 3 


85 


13-97 


14 


09 


28.0 


13-14 


13.26 


13 


38 


i3-5o 


13.62 


13 


74 


13 


86 


I 3 


98 


14.10 


14 


22 


•5 


I3.27 


13-39 


13 


5i 


13-63 


13-75 


13 


87 


13 


99 


14 


11 


14-23 


14 


35 


29.0 


J 3-39 


1351 


13 


63 


13-75 


13-87 


13 


99 


14 


11 


14 


23 


14-35 


14 


47 


•5 


13-52 


13-64 


13 


76 


13.88 


14.00 


14 


12 


14 


24 


H 


36 


14.48 


14 


60 


30.0 


13.64 


13.7613 


88 


14.00 


14.12 


14 


24 


14 


36 


14 


48 


14.60 


14 


72 


•5 


13-77 


13.89H 

! 


01 


14-13 


14-25 


U 


37 


14 


49 


14 


61 


14-73 


14 


85 


31.0 


13.89 


14.01 14 


r 3 


14-25 


14-37 


14 


49 


14 


61 


14 


73 


14.85 


14 


97 


•5 


14.02 14.14 14 


26 


14.38 


14.50 


14 


62 


14 


74 


14 


86 


14-98 


15 


10 


32.0 


14.14 14.26 14 


38 


14.50 


14.62 


14 


74 


14 


86 


14 


98 


15.10 


15 


22 


•5 


14.27 14.39 14 


5' 


14-63 


14-75 


14 


87 


14 


99 


15 


11 


15-23 


15 


35 


33-o 


H-39 


14.51 14 


63 


14-75 


14.87 


14 


99 


15 


11 


15 


23 


15-35 


15 


47 


•5 


14.51 14.63 14 


75 


14.87 


14.99 


15 


11 


15 


23 


15 


35 


15-47 


15 


59 


1034.0 


14.64 14.76.14 


88 


15.00 


15.12 


15 


24 


15 


36 


15 


48 


15.60 


15 


72 



n6 



WEIN'S TABLE FOR EQUIVALENTS OF LAC- 
TOSE, CALCULATED FOR USE IN 
SOXHLET'S METHOD. 



X 

o 
U 


H 

O 
H 
U 


as 

O 

b 

< 
fcn 


OS 
H 

Oh 
O 
O 


W 
O 

< 


« 
O 
H 
U 
< 


K 
M 

a, 
h 
O 
U 




h 
u 
< 


X 



H 
U 
< 


1 20 


86.4 


•73 


215 


158.2 


.76 


3IO 


232.2 


.81 


125 


90 


.1 


•73 


220 


l6l. 9 


.76 


315 


236.1 


.81 


130 


93 


8 


•74 


225 


I65.7 


.76 


320 


240.0 


.81 


135 


97 


6 


•74 


230 


I69.4 


.76 


325 


243-9 


.81 


140 


IOI 


3 


•74 


235 


I73-I 


.76 


330 


247.7 


.82 


145 


105 


1 


•74 


240 


176.9 


.76 


335 


251.6 


.82 


I50 


108 


8 


•74 


245 


I8O.8 


•77 


34o 


255-7 


.82 


155 


112 


6 


•75 


250 


I84.8 


■77 


345 


259.8 


.82 


l6o 


116 


4 


•75 


255 


188.7 


.78 


35o 


263.9 


.82 


I6 5 


120 


2 


•75 


260 


192-5 


•78 


355 


268.0 


.82 


170 


123 


9 


•75 


265 


I96.4 


.78 


360 


272.1 


.82 


175 


127 


8 


•75 


270 


200.3 


•79 


365 


276.2 


.82 


ISO 


131 


6 


•75 


275 


204.3 


.80 


37o 


280.5 


.85 


I8 5 


135 


4 


.76 


280 


208.3 


.80 


375 


284.8 


.85 


190 


139 


3 


•76 


2 8 5 


212.3 


.80 


380 


289.1 


.85 


195 


143 


1 


.76 


29O 


216.3 


.80 


385 


293-4 


.85 


200 


146 


9 


.76 


295 


220.3 


.80 


39o 


297.7 


.85 


205 


150 


7 


.76 


300 


224.4 


.81 


395 


302.0 


.85 


2IO 


154 


5 


•76 


305 


228.3 


.81 


400 


306.3 


.85 



LACTOSE TABLE. II 7 

The weights of copper and lactose (C 12 H 22 O n -(- H 2 0) are 
in milligrams. For amounts of copper intermediate be- 
tween those given in the table, the quantity of lactose is 
determined by the factor in the third column, which repre- 
sents the weight of copper corresponding to i milligram 
of lactose at that point. Thus, if 178 milligrams of cop- 
per are obtained, the calculation will be 178 — 175 = 3 ; 
3 X- 75 =2. 25 additional milligrams of lactose; 175 = 
127.8 .\ 178 = 130.00. The figure in the second decimal 
place in the product may be disregarded. The equivalent 
weights of copper and copper oxid are almost exactly in the 
ratio of 4 to 5, hence, if the weight is in terms of copper 
oxid, it may be converted into copper by multiplying by o. 8. 



Addendum to page 29. 

The mixture of amyl alcohol and hydrochloric must not 
be drawn into the measuring pipet by suction. It should 
be kept in a bottle provided with a pipet which can be filled 
to the mark by dipping, or the Greiner overflow-pipet may 
be used. Rigid accuracy in the measurement of the solu- 
tion is not needed. 

Addendum to page 4.6. 

N. Leonard {Analyst, June, 1896) finds that the addition 
of a trace of ferric chlorid to the sulfuric acid increases 
the delicacy of Hehner's test for formaldehyde. 



NDEX. 



A BNORMAL milks, 62 
•"■ Acetic acid test, 84 
Acid mercuric iodid, 72 
Adams' method, 23 
Adulterants of milk, 42 
Albumin, 10 

in condensed milk, 36 

, determination of, 35, 36 

Alumina cream, 72 
Amido-compounds, 103 
Ammonium compounds, 103 
Analytic processes, 18 
Annotto, 44, 62, 96 
Antiseptics, 45, 77 
Ash, 13, 22, 76 
Average solids in milk, 53 



TD ABCOCK'S method for solids, 

•^ Bacteria in milk, 15 

Baking soda, 50 

Benzoates, 47 

Birotation, 42 

" Black pepsin," 75 

Blue milk, 62 

Borax, 45 

Boric acid, 45, 48, 50, 52 

Breed, influence of, 56 

Butter, 75 

, calorimetric test for, 95 

, colors, 96 

, ether test for, 95 

, melting point of, 94 

, pan-test for, 95 

, specific gravity of, 94 

, yellow, 96 

Buttermilk, 17 



CALCULATION method, 29 
Cane-sugar, 44, 66, 70, 72 
Caramel, 44 
Carotin, 44 
Casein, 10, 75-6 
in butter, 75-6 



Casein, determination of, 35, 36 
Caseinogen, 11 
Cheddar cheese, 98 
Cheese, 97 

, analyses of, 99, 100, 104 

, cottage, 97 

, Dutch, 97 

, filled, 99 

, green, 97 

, proteid nitrogen in, 102 

, ripening, 97 

, skim-milk, 99 

, sour-milk, 97 

, Swiss, 97 

Chrome-yellow, 103 
Citric acid, 12 
Coloring matters, 44, 61 
Colostrum, 11-12-13 

corpuscle, 13 

Condensed milk, 64, 65 

, composition of, 64, 74 

Copper hydroxid mixture, 103 
Cream, 16 

evaporated, 64 

Curd of milk, 11, 17 



-p\ECOMPOSED milk, 18 

•*■*' Decomposition of milk, 15 

Diseases due to milk, 59 

Distillation method, 78, 81 

" Double dilution " method for sugar, 41 

Drought, effect of, 56 



i*NZYMESin milk, 12-16 

■* Evaporated cream, 64 



■pAT, 9 , 23, 66 

*• in butter, 75-6 

, extraction from cheese 

globules, 9 

t" ehling's solution, 37 
Fermentation method, 73 
Fermented milk products, 105 
Formaldehyde, 45-47, 51 



Il8 



Formalin, 45, 51 

Formula, Hehner and Richmond, 29 

, Richmond, 30 

Fluidometer, 92 
Freezing, effect of, 16 



GERRARD-ALLEX method, 70 
Globulin, 12 
Glycerol-soda, 78 



XJEHNER'Stest, 47 

•*■*■ and Angell's method, 

Hoppe-Seyler method, 35 
Hiibl's method, 85 



J^ITRATES in milk, 42 

QLEOMARGARIN, 76 
^■^ Oleorefractometer, 94 

PARAFORMALDEHYDE, 52 
■*■ Pavy's solution, 38, 68 
Poisonous effects, 16 
Polarimeters, 39, 71 
Polarimetry, 39 
Preservaline, 52 
Preservation of samples, 51 
Preservatives, 45, 51 
Proteids, 10, 66 

, determination of, 31 

Pyknometer, 20 



TNSOLUBLE acids, 88 
•*■ Inversion of sucrose, 67 
Invenase, 67 
Invert -sugar, 72 
Iodin number, 85 



T7-EFYR, 106 

■**• Kjeldahl-Gunning method, 
Koettstorfer number, 90 
Kumiss, 105 



T ACTALBUMIN, 10, n 
■*-' Lactodensimeter, 19 
Lactometer, 19 
Lactose, 12, 66 

, table for, 117 

Leffmann Beam method, 26, 



TWTARGARIN, 76 
■ LVA Martius' yellow, 44 
Methyl aldehyde, 45 
Microbes in milk, 15 
Milk, abnormal, 55 

adulterants, 42 

, blue, 62 

, composition of, 53 

inspection, 53 

, nature of, 9 

Milks of various animals, 
Milk products, 64 

, red, 62 

, ropy, 62 

scale, 30 

standards, 54, 57-8 

sugar, 12, 66 

, variations in, 52 

Mineral matters of milk, 



RECKNAGEL'S phenomenon, 15, 18 
Red milk, 62 
Refractive index, 93 
Reichert method, 78, 81 
Rennet, 97 

, action of, 11 

Rennin, 97 
Richmond's ratio, 43 
Ritthausen method, 33-4, 35 
Ropy milk, 62 



e ALICYLIC acid, 45, 50 
° Salt, 45, 75-6 
Sanitary relations, 58 
Saponification, 81 

equivalent, 90 

flasks, 81 

Schiff's reagent, 46 
Season, influence of, 57 
Separator milk, 17, 59 
Skim-milk, 59 
Slide-rule, 29 
Sodium benzoate, 45 

acid carbonate, 50 

carbonate, 45, 50 

Solids, deficiency in, 55 

, excess of, 55 

Soluble acids, 88 
Sour milk, analysis of, 25 
Soxhlet's method for lactose, 37 
Specific gravity, 19 

, change in, 15, 18 

Specific rotatory power, 40 

Starch, 44 

Sterilized milk, 15, 60 

Sucrose, 66, 70, 72 

Sugar of milk, determination of, 37 



"» ABLE for lactose, 116 

for temperature, 107 

for total solids, 111 



Temperature, correction for, 107 
Thomson's method, 49 
Total proteids, 31, 33 

solids, 21 

solids calculated, in 

solids, decrease of, 18 

Tuberculosis, 59 



V 



ALENTA'S test, 84 
Vieth's method for solids, 
- ratio, 43 



Viscosimeter, 91 
Viscosity of butter, 91 



\A7ATER in butter, 75-76 

V " in milk, 42 

Werner-Schmid method, 25 

Westphal balance, 19 

Whey, 17 

Wiley and Ewell's method for sugar t 41 

Wiley's method, 38 



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